where p is the principal invested, r is the interest rate as a decimal number, n is the number of times the interest is compounded yearly, and t is the amount of time.
Let us try and solve it analytically. We have that the side=x+3 together with the short side=s and the diagonal=x+4 satisfy the Pythagorean Theorem. Then we have that . This yields which yields s^2=2x+7, hence a) is the correct answer.