How do I solve this?

Question

A toxic chemical decays with a half-life of 7 years, so half of it will be gone 7 years from now and then half will be gone 7 years after that. This statement does or does not make sense? After 14 years, the toxic chemical will decay to an amount equal to ______ times the original amount

Answer 1

fraction left after 14 years = 1/2 times 1/2

1/4= 25% of the original amount will be left

3/4 = 75% gone in 14 years if half life is 7 years

.5^n/7 is left after n/7 years if half life = 7 years

for n =14 .5^14/7 = .5^2 = .25= 25% = 1/4 left after 7 yeaars