Question 389582
"there are 4 more girls than boys" ___ g = b + 4


"5/7 of the boys and 2/3 of the girls take the floor for the first dance" ___ 5b / 7 = 2g / 3 ___ 15b = 14g


substituting ___ 15b = 14(b + 4) ___ 15b = 14b + 56 ___ b = 56