Answers by visitors named: Chris S.

In this particular case, the problem tells you that both formulas equal 20. This means that 3x+5y = -2x +5y. If you put the ys on one side and the xs on the other, the 5ys disappear. 3x + 5y -5y = -2x + 5y -5y (what you do on one side, has to be done on t...

Thanks. Much appreciated.