Question

Solve the system using substitution.

3x – y = -1
x – y = -3

What is the solution for y?

Answer 1

if you want y, you need to replace x

what is an equation for x using the second part?

Answer 2

You could also change the sign of the second equation and add it to the first.

Answer 3

solution by method tho ... but yes, that would eliminate the ys and solve for x; and backtrack to get ys again

Answer 4

x=y+3?

Answer 5

very close, assuming a typo - x = y - 3

Answer 6

lets use this equation in place of the "x" up top; that will give us just ys to play with

3x – y = -1

3(y-3) – y = -1

Answer 7

the rest is just basic order of operations to get to y

Answer 8

so then, it would be
3y-9-y=1
3y-8-y
4y=-8
y=-2

Answer 9

lets see if we can follow that thru:

3y-9-y=1 <<< and this one needs to be = -1, careful with those
3y-8-y << this ones off a bit

3y-9-y=-1 : commute
3y-y-9=-1 : combine like terms
2y-9 = -1 : +9 both sides
2y = 8 : divide off the 2
y = 4

Answer 10

oh

Answer 11

keep up the practice ;)

Answer 12

Thanks