So we are looking for the P also known as principle. Fill in the equation with what we know. Remember, r = rate (so your percentage) and t = time (so number of years)
354.18 = P(1 + 0.09)^2
Divide both sides by (1 + 0.09)^2
298.106 = P
Round that up because we're dealing with money to get a principle of $298.12