Answer:
-11 is your answer.
Step-by-step explanation:
Total measurements of interior angles in a triangle = 180°.
Note that the red square located on the bottom right angle signifies that it is a right angle, with a measurement of 90°. Set the equation:
Total measurement = (90) + (70) + (x + 31)
180 = x + (90 + 70 + 31)
180 = x + 191
Isolate the variable, x. Note the equal sign, what you do to one side, you do to the other. Subtract 191 from both sides:
180 (-191) = x + 191 (-191)
180 - 191 = x
x = - 11
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