Alan, Benny and Charles had a total of $750 at first. Alan gave $30 to Benny. Benny gave $50 to Charles. Each of them then had the same amount of money. How much money did each boy have at first?
+600 $a+b+c=750$
$a-30, b+30, c$
$a-30, b-20, c+50$
$a-30=b-20=c+50$
Solve.
