Throughout the first part of the paper, we addressed the question "Why do we learn algebra", and listed ways of introducing algebra into teaching since the first encounter is pre-eminent for the development of a positive attitude towards algebra. From the very beginning of learning algebra, besides practicing manipulation with algebraic expressions, it is important to present a variety of real-life examples to help students understand how algebra helps them solving different problems. In the second part of the paper, we have demonstrated the interlink of algebra and geometry. Student accepts graphics display with ease because they provide a better insight into the meaning of different algebraic expressions. On the other hand, students realize that algebra is a powerful tool for solving all sorts of geometric problems. We have demonstrated how algebra is used in the isosceles triangle and how it helps us calculate the angles of a polygon, perimeter, and area of different shapes. We have also demonstrated how real-life problems are solved by using the interlink of algebra, similarity of the triangle, and Pythagorean theorem. The third part of the paper deals with algebra and trigonometry. Since students often have a negative attitude towards trigonometry, mainly because they perceive it as a large number of formulas with meaning, it is important that from the first encounter with trigonometry students understand the concepts of sinus, cosine, and tangent, and only then should the formulas be derived from known facts in order for students to be able to perceive their meaning. The paper shows how to introduce the concepts of sinus, cosine, and tangent to the teaching, and how to solve several trigonometric problems. The paper also shows how to get acquainted with the Sinus and Cosine theorems and to perform several trigonometric identities. In addition, there are some real-life examples of how should the students perceive the application of trigonometry, which develops a positive attitude and motivation towards learning trigonometry.