Let the number of Boys in Group 1 be x. The number of girls in Group 1 is therefore 40-x. and the number of girls in group 2 is 33 ? (44 ?x) = x ? 7.

There are therefore 7 fewer girls in group 2 than boys in group 1.

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.