Which expression represents the phrase, "One-third the sum of 12 and a number?

a.) 1 /3 ( 12 ) + x
b.) 1 / 3x + 12
c.) 1 / 3 + 12 + x
d.) 1 / 3 ( 12 + x )

Taber invested money in an account where interest is compounded every year.he made no withdrawals or deposits. the function a(t)=525(1+0.05)^t represent the amount of money in the account after t years. how much money did taber origanally invested?