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That exterior angle is equal to 87 degrees.

Step-by-step explanation:

In order to find the measure of the exterior angle, we start by trying to find x. We can do this by adding up the 3 interior angles and setting them equal to 180. The first angle is equal to 43. The second angle is equal to x + 15. The third angle is equal to 180 - 3x (which we know because the angle and 3x is equal to 180). So we set equal to 180.

43 + (x + 15) + (180 - 3x) = 180 > Combine like terms.

238 - 2x = 180 > Subtract 238

-2x = -58 > Divide by -2

x = 29

Now that we have the x value, we can plug into the exterior angle measure to get the value.

3x = 3(29) = 87 degrees