How can 7 1/5 + -8 3/5 be expressed as a sum

At the beginning of 1974/75,2 years a man invested #2000 in a bank at 12.5% compound interest, if it degree #650 at the end of each two years to pay his son's school fees, after payment of interest to pay his son's school fees, how much did he have left at the beginning of the 1978/79 school year?

Solve this problem! extra ! 3025/5.5 = a/90.75

If the perimeter of the garden is 37 ft. the width is x and the length is 15 ft. what is the width of the garden in feet?