I don't know what you mean by equation 1. I assume you mean x + y = 7 is equation 1.
If so, solve for y as step 1.
x + y = 7
y = - x + 7
The y-intercept is 7.
Your directions do not say to solve the system of equations.
If you need to solve by graphing, use DESMOS or your graphing calculator. The solution of the system of equations is the point on the graph where the two equations meet or touch each other.