Answer:
40
Step-by-step explanation:
You know that angle m<SRT is 40, because it's a supplementary angle with 140. 180 - 140 = 40.
Next, you also know that the interior angles of a triangle add up to 180, so you would now make an equation adding all three angles and setting them equal to 180.
40 + 3x + 4 + 8x + 4 = 180
You would now add like terms.
11x + 48 = 180
You would now subtract 48 from both sides.
11x = 132
You would now divide both sides by 11.
x = 12
You would now plug x into m<RST, 3x + 4.
3(12) + 4 = m<RST
36 + 4 = m<RST
40 = m<RST
