Complementary angles are two angles whose measures add up to 90 degrees. In this case, angle ZABC measures 63 degrees. To find the measure of angle DEF (which is represented by x), we can use the equation: x + 63 = 90. By subtracting 63 from both sides, we find that x = 90 - 63, which simplifies to x = 27 degrees. Therefore, the measure of angle DEF is 27 degrees.