Recent introduction of modern computer technology into schools and universities presented new challenges to mathematics teachers. On one hand, powerful computer tools have emerged that allow for rich animation and visualization. On the other hand, the teachers are not ready to give up using the blackboard, which is still their main workspace. This work presents a tool for teachers, that allows for more freedom than the fixed lecture slides and helps illustrating rules for transforming mathematical expressions and solving equations. Using this tool, the teacher can automatically generate solutions for mathematical problems on the fly and interactively present these to the students step by step. The solution is then blended out and the students are offered to solve similar problems on their computers interactively using the system. This tool is a part of a larger toolkit used within several innovative Blended Learning Bridging Courses in Mathematics at Leuphana University in L¨uneburg, held in a computer-equipped classroom.