Sylvie solved this system of equations. y = 5x + 2,

y = 8 – x

8 – x = 5x + 2

8 = 6x + 2

6 = 6x

x = 1

8 – 1 = 5(1) + 2

7 = 7

There are infinite solutions to this system.

When Sylvie verified the solution on a graph, the lines intersected at one point. What was her error?
She forgot to put both equations in slope-intercept form.
She made an arithmetic mistake in the last step.
She found the incorrect value of x.
She did not substitute the value of x into one of the original equations to find y.