74.4 grams of the new compound will be formed.
The weight ratio at which the two elements P and Q combines is 1:5. So for every 1 gram of P there is 5 grams of Q.
Here we are supplied with 15 grams of P. So Q needed for 15 grams of P is 75 grams which we don't have.
We are given with 62 grams of Q. So P needed for that amount of Q is 12.4 grams.
Thus the compound will weigh [tex]62 + 12.4[/tex] grams which will give us with 74.4 grams of compound.