X-3 when x = 5 plz answer for math grade 5

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.

At 6 1/2 cents per pound of string beans how much does 7 pounds cost

Can someone show me step by step how to do this?