(1,10) satisfy the first equation and the second equation.
Since the x-coordinate is 1 and the y-coordinate is 10, you can plug these numbers in for the x and y of the equation like this:
10 = 1 + 9
10 = 10
This satisfy the first equation of y = x + 9
10 = 9(1) + 1
10 = 10
This satisfy both of the equations, so this is a solution to this system of equations.
LOL! I was in eighth grade last year, I understand the struggle! ._.