Question

os ângulos ABC e CBD São complementares determine X

Answer 1

$3x + x - 12 + 42 = 90 \\ 4x + 30 = 90 \\ 4x = 90 - 30 \\ 4x = 60 \\ x = \frac{60}{4} \\ x = 15$
$x = {15}^{0}$