Asked by Anonymous

solve by substitution method
y=x-4
6x-9y=21
Answered by jen
-x+y=-4
6x-9y=21
multiply the top row by 6
-6x+6y=-24
6x-9y=21
-3y=-3
y=1
put 1 back in either equation for y
i put it in the first one
1=x-4
x=5
Answered by jen
Oh sorry, i just realized it said to use substitution and I used elimination. I forgot how to do substitution.
Answered by Reiny
just sub in the first equation into the second

6x - 9y = 21
6x - 9(x-4) = 21
6x - 9x + 36 = 21
-3x = -15
x = 5
then y = 5-4 = 1
Answered by Anonymous
-2x+4y=-4 and 6x + 6y = -24