The sum of the angles of a triangle always equals 180°, then we can formulate the following expression:
(x + 69)° + (39 + x)° + 90° = 180°
By combining like terms in the above equation, we get:
x + x + 69 + 39 + 90 = 180
2x + 198° = 180°
We can solve for x to get:
2x + 198 - 198 = 180 - 198
2x = 180 - 198
2x = -18
x = -18/2
x = -9
Then, x equals -9.
In order to calculate the measure of angle A, we just have to replace the value of x into the equation 39 + x, then we get:
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Then, the measure of angle A equals 30°.