Question 1013213
Even investing the entire 400 pesos at the higher rate (5%) 
would only yield 20 pesos per year. To have an income of 
168 pesos from 400 pesos:
400x=168
x=168/400
x=0.42
(0.42)(100%)=42%
.
He must earn an interest rate of 42%.
There is no solution to this problem as given.