"A" = amount you will ultimately have in the account (A=1200+200=1400)
"P" = amount you started with, aka principal (p=1200)
"i" = interest rate per year (i=9%)
"m" = number of compounding periods per year (Quarterly means m=4)
"n" = number of years (n=??? - this is what you're solving for)
Plug into the formula and solve for N.
So it takes approx 1.732 years (20.78 months) to earn $200 of interest.