Asap 9th grade math and i need , 15 points and brainlist

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:

x = 40°