Answer: 4 years
Step-by-step explanation: Begin by writing the interest formula.
Interest = principal x rate x time
Filling in the formula, the interest is $252, the principal is $900, the rate is 7% or .075 and we don't know the time so we use the variable t.
252 = (900)(.07)(t)
On the right side of our equation, we multiply 900 times .07 to get 63 and we have 252 = 63t. Now to solve for t, we divide both sides of the equation by 63 to get 4 = t which means that our principal must be invested for 4 years to earn $252 in interest.