Find the total balance of each investment account earning simple annual interest. a: $624 at 5% for 3 years
b: $4,120 at 7% for 18 months
c: $900 at 3.1% for 6 months
d: $275 at 4.8% for 8 years

You should remember the formula: Interest = P * R * T /100
Apply it in every part.

A) I = 624 * 5 * 3 / 100
   I = 9360/100
  I = 93.60
So, Total amount = 93.60 + 624 = $717.60

B) I = 4120 * 7 * 3 / 2*100
  I = 86520 / 200
  I = 432.60
So, Total amount = 432.60 + 4120 = $4552.60

C) I = 900 * 3.1 * 1 / 2 * 100
 I = 2790 / 200
I = 13.95
So, Total Amount = 13.95 + 900 = $913.95

D) I = 275 * 4.8 * 8 /100
 I = 10560 / 100
 I = 105.60
So, Total amount = 105.60 + 275 = $380.60

Hope this helps!