In what time will $400 amount to $512 if the simple interest is calculated at 14% p. a.

The time is 2 years:

Important variables to know:
A= Amount
P = Principal
I = simple Interest
T = time in years
R = rate in years

Formulas:
A = P + I
I = PRT

What we have? Amount ($512), Principal ($400), Rate (14%)
What we need? Time and Interest (simple interest)

So, first let's find the interest.

512 = 400 + I
Subtract 400 from both sides.
I = 112

Then plug that into the second formula:
112 = 400*.14(T)
Multiply 400*.14= 56
112 = 56T
Divide both sides by 56
T = 2 years