Please someone help me! This is the formula A=Ao2^-t/h. If A is the amount of radioactive material present at?

... time t, Ao was the amount present at t=0, and h is the material's half-life, then A=Ao2^-t/h. Does anybody know how to apply this problem to the previos formula? Heres the problem: The half life of a radioactive isotope is 7 days. If 5.6 are present now, how much will be present in 14 days?... please help me. i dont understand this :/