A country seen its population grow each year than 1/8 it was last year. At that time the population will have doubled and tripled
1/8 = .125 or 12.5%
so to double we would solve
1(1.125)^n = 2
log both sides
log (1.125^n = log2
n log 1.125 = log2
n = log2/log 1.125 = appr 5.885 years
for tripling, solve
1.125^n = 3 ------> you should get appr 9.33