How many 2 digit numbers do not use the numeral 5?

Create a real-life situation and create a system and show how it might be modeled algebraically with a system of equations (or inequalities) show all work include a few sentences explaining the situation, your variables of choice and what each represents, and how you would set it up and solve it algebraically. !

Sam claims that cos x =sin y if x and y are congruent angels. is sam correct ?

Does anyone know how to do geometryme with this problem