so we know that A+B+C= 72. We also know that B=2A (1) and C=3B which means C=6A (2) and with this information we can re arrange to equation to be only have one variable. so A+2A+6A= 72 Collecting all the terms we get: 9A= 72so A=8subbing this into equation (1) and (2) we getB=16 and C=48
we can then check if our answer is correct by subbing the numbers into the original equation A+B+C= 728+16+48=72, which is correct.