Answer:
x = 40°
Step-by-step explanation:
Given that ∠SRT ≅ ∠STR
Then ∠STR = 20
∠STR and ∠STU are what you call supplementary angles. This means that the sum of their measurements is equal to 180° because they form a straight line.
So if:
∠STR + ∠STU = 180°
m∠STU = 4x
m∠STR = 20
Then:
4x + 20° = 180°
Now we solve for x:
[tex]4x + 20 = 180\\\\Subtract\;20\;from\;both\;sides\;of\;the\;equation\\\\4x + 20 - 20 = 180 - 20\\4x = 160\\\\Divide\;both\;sides\;of\;the\;equation\;by\;4\\\\\dfrac{4x}{4}=\dfrac{160}{4}\\\\x = 40[/tex]
x = 40°
