If it's simple interest, it's 6% or 6/100=3/50 of the amount invested over one year: 3*1200/50 or 6*1200/100=$72 interest, making $1272 in the account after a year.
If it's compound interest compounded each year, then the answer is still $72 for one year. If interest is compounded every month the total amount after a year is 1200*1.005^12=$1274.01. (1.005=1+6%/12=1+1/2%=1.005.)
If interest is compounded quarterly, we divide 6% by 4=1.5%=0.015 and the amount after a year would be 1200*1.015^4=$1273.64.