The value of the function f(x) is 15/2 when x = -5 and is - 72/2 when x = 3. What is the equation of the function?

Ireally need ! if a musician uses his credit card to pay for a new violin that costs $2,900 and does not pay on it until the second month, what will the 3.35% monthly interest charge be at the end of the first month? show your work or explain how you got your answer.