Problem: solve for x and y in x+y=8
this will be used to solve measurements in a geometry question.
What you have there amounts to a linear equation:
x + y = 8
x + y - x = -x + 8
y = -x + 8
Graphing this produces a straight (linear) line.
You can choose any value for x, plug it into the equation,
and get the corresponding value for y.
If you were to choose x = 0, y would be 8. That is how we
find the y-intercept on the graph. (0, 8)
If you choose 8 for x, y would be 0. y = -8 + 8
(The negative represents -1, the slope of the line.)