Answer:
∠B = 54 °
Step-by-step explanation:
If sum of two angles add up to 180°, then the two angles are called supplementary.
m∠A + m ∠B = 180°
7x + 7 + 4x - 14 = 180
7x + 4x + 7 - 14 = 180
11x - 7 = 180
11x = 180 + 7
11x = 187
x = 187 ÷ 11
[tex]\sf \boxed{x = 17^\circ}[/tex]
m∠B = 4x - 14
= 4*17 - 14
= 68 - 14
[tex]\sf \boxed{\bf \angle B = 54^\circ}[/tex]
