What do you need to know so what I don’t know is math

Yea

For how answer my question this will be the last question can you answer in math subject

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.

Which of the following is the true for f(x) = 5cos