5x+7y=3 2x-4y=8 How much is? In matching theory With process

5x+7y=3

2x-4y=8       note that.....dividing both sides by 2, this reduces to x - 2y = 4   add 2y to both sides x = 4 + 2y

Replacing this for x in the first equation, we have

5(4 + 2y) + 7y = 3   simplify

20 + 10y + 7y = 3

20 + 17y = 3         subtract 20 from both sides

17y = -17             divide both sides by 17

y = -1

And using  x = 4 + 2y  → x = 4 + 2(-1)   → x = 4 - 2   =  2

So...the solution is  x = 2 and y = -1