How do I do this and what is the correct answer?

Determine the relationship of ab and cd given the following points

What two criteria are needed for triangles to be similar

Marco has $38.43 dollars in his checking account. his checking account is linked to his amazon music account so he can buy music. the songs he purchases cost $1.29. part 1: write an expression to describe the amount of money in his checking account in relationship to the number of songs he purchases. part 2: describe what the variable represents in this situation.