Answer:
∠A= 111.75°
Explanation:
Please see the attached picture.
∠B +∠C= 180° (adj ∠s on a str. line)
(x +35)° +∠C= 180°
∠C= 180° -(x +35)°
∠C= 145° -x°
∠A= ∠C (corr. ∠s)
∠A= 145° -x°
Given that ∠A is (3x +12)°, equate this expression to the expression we found.
145° -x°= 3x° +12°
3x° +x°= 145° -12°
4x°= 133°
x°= 133° ÷4 (÷4 on both sides)
x°= 33.25°
Substitute the value of x back into the expression for ∠A:
∴∠A= 3(33.25°) +12°
∠A= 111.75°