Question

Solve system of equations using substitution x=7y and 3x+2y=23

Answer 1

Since you know x = 7y
Then you basically plug in 7y in the second equation in place of x
So then you get 3(7y)+2y=23
And 3 x 7y = 21y
So now your equation is 21y + 2y = 23
And 21y + 2y = 23y
So now your equation is 23y = 23
Then divide both sides by 23 to get y alone
And you should get y = 1

Now that you know y=1
So plug 1 in place of y in either of the equation
I chose the first one since it is easier
So when you plug in 1,
Your equation is now x = 7(1)
And 7 x 1 = 7
So x = 7


So the solution is ( 7, 1 )

Answer 2

x=7y

3x+2y=23 plug 7y into this equation's x

3(7y)+2y=23 multiply 3 and 7

21y + 2y=23 add 21y and 2y together

23y=23 divide both sides by 23

y=1 then plug y into one of the given equations, either one it doesn't matter but I would use x=7y cause it's easier
x=7(1)

x=7

so, x=7 and y=1