Problem solving is a very important part of learning mathematics, with problem solving students can practice and explore concepts, theorems and skills. So, the problem solving can improve students’ abilities and understanding in mathematics (Hudojo, 2005). Since 2006 Indonesia has begun implementing problem solving in student learning activities, this form of implementation is more focused on scientific approaches, This is intended so that students can have high-level knowledge and skills (Permendikbud (54), 2013).

HOTS achievement can be influenced by several factors, namely internal and external factors. Internal factors include students’ interests and motivations in learning mathematics (Lazarides & Ittel, 2012; Sukada, 2013; Maurice, Dorfler & Artelt, 2014; Sumantri & Whardani, 2017; Surifah, 2016; Tambunan, 2018). Whereas external factors, namely implementing a scientific approach to learning (Al-Agili, 2012; Justice, Agyman & Nkum, 2015; Margaret, 2015; Sa’ad, 2014). According to Polya (1973) there are four stages of the problem solving method, namely:

- We must understand the problem,
- Develop a plan or step to solve the problem,
- Implement the plan, and
- We must correct it.

Whereas in mathematics education what is meant by high-level thinking skills is in the form of communication skills, creativity, problem solving and mathematical reasoning (Brookhart, 2010; Honey, 2017; Setiawan, 2014; Tambunan, 2018; Wardhani, 2015). communication referred to in mathematics is the ability to convey ideas in mathematical language (Baroody, 1993). While what is meant by creativity here is the ability of a person to choose solutions in solving mathematical problems (Sriraman, 2011).

Mathematical problems are nothing but mathematical story problems where we know that story problems do not have clear rules to solve them so students are required to have the ability to predict, analyze and reason to solve them (Baroody, 1993; Hudoyo, 2005; James, 1976; Tambunan, 1999 ; Anderson, 2009). Mathematical reasoning is the ability to produce statements from a thought so that it can produce a conclusion to solve mathematical problems (Lithner, 2008).

The method used in this study is pseudo research. This research was conducted on some 10th grade public and private high school students in Medan-Indonesia, where students were divided into two groups, namely the experimental group and the control group, then the two groups were given the pretest and posttimes in the form of essay questions because they were considered the effectiveness of problem solving strategies and scientific approaches. and students are instructed to solve the problem.

The experimental group is students who are taught by two teachers with problem solving strategies, while the control group is students taught by two teachers with a scientific approach. Students in the experimental group amounted to 138, while in the control group there were 139 students. In this study there were four classes, two classes came from public schools and two classes came from private schools with random sampling. This study uses ANOVA and t test using the SPSS application.

The results of data analysis using SPSS indicate that the experimental group has a higher value than the control class. The result of the conclusion of the t test hypothesis also shows that the null hypothesis is rejected which means that problem solving strategies are more effective than scientific approaches in various mathematical skills, namely communication skills, creativity, problem solving and reasoning. The results of this study are in accordance with the results of previous studies that have been proposed by several people.

From several reviews of research on high school students, we can know that solving strategies are more effective when compared to scientific approaches to improving students’ HOTS abilities which include communication skills, creativity, problem solving and reasoning. Therefore it would be better if the problem solving strategies were used in teaching, compared to the scientific approach.