let 'A' represent accumulated total, 'p' represent principal, 'r' represent rate, 'n' represent number of times per year compounding is performed and 't' represent number of years of compounding

A = p(1+r/n)^(nt)

principal starts at $750, therefore we want A=750*3=2250

compounding quarterly, therefore n=4

we want to solve for 't':

2250 = 750(1+0.032/4)^(4t)

solving for 't' we have t=34.468

it will take approximately 34 and 1/2 years for the investment to triple