Solving systems of equations by substitution

Equation 1)  2x - 3y = -1
Equation 2)  y = x - 1

We want both equations to be in standard form (Ax+By=C) so we need to fix the second equation.

For the second equation, simply subtract x from both sides, so that x & y are on the same side of the equal sign :)

2)  -x + y = -1
1)  2x - 3y = -1

Now, we have to multiply ALL of equation 2 by 2 so that both equations 1 & 2 have "2x" in them :)

2)  2(-x + y = -1)

Simplify.

2) -2x + 2y = -2
1)  2x - 3y = -1

Now, add these equations together.

-y = -3

Divide both sides by -1.

y = 3

Now, plug in 3 for y in the first equation.

1)  2x - 3y = -1

2x - 3(3) = -1

Simplify.

2x - 9 = -1

Then, add 9 to both sides.

2x = -1 + 9

Simplify.

2x = 8

Divide both sides by 2.

x = 4

So, x = 4 & y = 3

~Hope I helped!~

Cd is the perpendicular bisector of both xy and st, and cy=20.find xy