GH = 68
Lets take it through the process. We first have to figure out what G and H equal to separately.
In order to get 8, they could use the following equations; 1 x 8 , 2 x 4 , 4 x 2 , 8 x 1
In order to get 34, they could use the following equations; 1 x 34 , 2 x 17, 17 x 2 , 34 x 1
Taking the highest numbers, we can say that F = 2, G = 4, and H = 17.
Therefore, GH = 68