I think the end of the question is "g" not "c". To get the offspring wanted, there are two types of genotype, one is TTgg, the other one is Ttgg. The chance of getting TT or Tt is 1-(1/2)*(1/2)=3/4. The chance of getting gg is (1/2)*(1/2)=1/4. So the total chance is (3/4)*(1/4)=3/16.