In this paper we are emphasizing the importance of developing algorithmic thinking, for improving problem solving skills. Problem solving competence is important for one of the eight key competences defined at EU level - mathematical competence. We will find a relationship between Polya's problem-solving and algorithmic thinking, comparing basic Polya's principles to definition of algorithmic thinking. So, we are considering algorithmic thinking as an important role in high school education for developing mathematical competence. We are using crocheted geometrical shapes and finding a mathematical model to realize it through crochet. We developed algorithms for crocheted models, as a useful educational tool.