11. x = 16 complementary angles add up to 90°. angle 1 and angle 2 added together will equal 90°. 42 + 3x = 90 subtract 42 on both sides. 3x = 48 divide by 3 on both sides. x = 16 12. x = 26 supplementary angles add up to 180°. angle c and two times the value of x (2x) will equal 180°. 128 + 2x = 180 subtract 128 on both sides 2x = 52 x = 26 hope this helps!
