We know: The sum of the measures of the angles of a triangle is equal 180°.
We have: m∠A = (6x - 1)°, m∠B = 20° and m∠C = (x + 14)°.
The equation:
(6x - 1) + 20 + (x + 14) = 180
(6x + x) + (-1 + 20 + 14) = 180
7x + 33 = 180 subtract 33 from both sides
7x = 147 divide both sides by 7
x = 21
m∠A = (6x - 1)° → m∠A = (6 · 21 - 1)° = (126 - 1)° = 125°
m∠C = (x + 14)° → m∠C = (21 + 14)° = 35°
Answer: m∠A = 125°, m∠C = 35°
