Point Q lies in the interior of ∠RST. If m∠RST = 125°, m∠RSQ = 4x − 7, m∠QST = 11x + 12, then find x.
Since Q lies in the interior of ∠RST, the sum of ∠RSQ and ∠QST must equal ∠RST.
m∠RSQ + m∠QST = m∠RST
(4x - 7) + (11x + 12) = 125
15x + 5 = 125
15x = 120
x = 8
Therefore, x = 8.