John has 13 balls less than Peter, and they have 31 balls between them. How many has each of them?

Question

Word problem involving use if symbols

Answer 1

Well if John has 13 balls less than Peter, then if $J$ is John's balls and $P$ is Peter's, we get $J=P-13$

But then the total balls are $31$, that is $J+P=31$

We then make the substitution from the first line so: $(P-13)+P=31$