How do I add exponent denominator and numerator

On a piece of paper graph f(x)=5•(0.4)^x

Simplify 24÷(-2)(3)+7 a. -29 b. 3 c. 11

Margaret is purchasing a house for $210,000 with a 15 year fixed rate mortgage at 4.75% interest she has made a 5% down payment the house is valued at 205,000 and the local tax rate is 3.5% homeowners insurance 600 per year what are her total monthly payment