so to use the method of substitution
we are given that y = 3x -1
and that y = -4x + 20
to substitute we will plug in the second equation to substitute for the y in the first
-4x + 20 = 3x - 1
now we can add 4x to both sides (this is to bring common terms together)
20 = 7x - 1
add 1
21 = 7x
now to isolate the variable x
divide both sides by 7
21/7 = x
or
3 = x
Now that we know that x = 3 we can plug that into any of the two given equations to solve for y
y = 3(3) - 1
y = 9 - 1
y = 8
There you have it... x = 3 and y = 8
Hope this helps :)
