You have 2 equations that are both equal to y. If they are both equal to y, then by the transitive property of equality, they are equal to each other (if a = b, and b = c, then a = c).
5x - 17 = x + 3 and
4x = 20 and x = 5. Now sub in that x value of 5 to solve for y:
y = 5 + 3 and y = 8. So the ordered pair is (5, 8)