Answer:
Sum of money = $600
Explanation:
X = sum of money
Simple interest means that its the same percentage of interest for a given number of years.
The interest per annum is 5% for 3 years, so 5% x 3 = 15%
15% = 0.15 (as a decimal)
Now, we can put this into an equation:
0.15x = 90
x = 90 / 0.15
x = 600.
sum of money invested = $600