1) for this exercise you must apply the following formula,
I = C ×i×n, where I is the interest, C is the capital initial, i is the rate of interest, and n is time
2) second step
you must× calculate the I = M-C, where M is the final amount and C is the capital
I = 578-500 = 78
3) third step
substitute the values in equation 1
I = C ×i ×n
78= 500×i×3⇒i =78/(500×3)⇒i= 0,052 ⇒ 0,05×100 = 5,2% annual interest
