Help me please this question is about shapes and tree diagrams

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.

Use composition to determine if (x) or h(x) is the inverse of f(x) for the limited domain x2-1.

For f(x) = 3x+1 and g(x) = x2 - 6, find (g/f)(x)