It is 15 because 5 times 3 is 15
Since complementary angles add to 90°, (4x - 1) and (5x + 19), also add to 90°.
Thus, lets form an equation:
90 = 5x + 19 + 4x - 1
72 = 9x
x = 9
Thus, the measure of angle B is 64°.
4m+2
because 2mx2=4m and 1x2=2 so 4m+2