David weighs 20lbs.more than katy ,while Jonathon weighs 120lbs. less than three times katy's weight. If David and Jonathon weigh the same amont , how mush does katy weigh? How much much does David and Jonathon weigh?

2 answers

I think it is 42 I don't know
Katy' weight --- x
David ------ x+20
Jonathan --- 3x - 120

3x-120 = x+20
2x = 140
x = 70

sub back into my definitions for their weights

Tell me how you got 42 ??