Respuesta :

Supplementary angles are angles that add to 180 degrees......in this case "x" would equal 22
Supplementary angles add up to 180 degrees.

m∠1 + m∠2 = 180° 
(3x - 17) + (5x + 21) = 180
8x + 4 = 180
8x = 176
x = 22

The value of x is 22 degrees.