Question

Solving systems by substitution:
3x+y=2
4x+y=20
I don't understand how to solve it

Answer 1

First equation.
3x+y=2
-3x. -3x
_________
y=-3×+2

second.
4x+y=20
-4x. -4x
________
y=-4x+20

-3x+2=-4x+20
+3x. +3x
____________
2=-x+20
-20. -20
-18= -x
__ ___
-1. -1
18=x

Then you would go back to the original equation and substitute 18 for X

Answer 2

Basically solve for y first

3X + Y = 2

Subract 3X

Y = -3X+2

Same with the other equation


4X+Y=20

Subract 4X

Y = 20-4X


Set the equations to each other and then solve


20-4X= -3X+2

Add 4X

20=X+2

Subract 2


X = 18

And now plug in 18 to one of the equations

3(18)+Y = 2

54 + Y = 2

Subract 54 on both sides

and the answer is -52

(18,52) is the answer