y = x + 3
2x + y = 9
substitute the first equation into the second equation;
2x + y = 9
2x + x + 3 = 9
3x + 3 = 9
solve for x;
3x + 3 = 9
3x = 9 - 3
3x = 6
x = 2
solve for y, given the value of x;
y = x + 3
y = 2 + 3
y = 5
so the answer is (2, 5).
hope this helps, God bless!