Question

What is the y-coordinate of the solution to the following system of equations?

y=2x + 1
x+y = 1

Answer 1

Answer : y coordinate is 1

y = 2x + 1

x + y = 1

solve for y : x + y = 1

-x -x

y = -x + 1

Graph them,

(0,1) (x,y) y value is 1

Answer 2

You know that y=2x+1 because it is a given equation. Therefore you can plug (2x+1) in for y in the second formula.
This will give you:
x+(2x+1)=1
3x+1=1
3x=0
x=0

Now that you know x, you can plug it into either equation to find y.
y=2(0)+1 (0)+y=1
y=1 y=1