Question 1173949
Let x = the angle<br>

Then complementary angle is 90-x<br>

Assume x is the larger angle:
x - (90-x) = 30<br>

2x - 90 = 30

Solve for x, 90-x to get the two angles (60 and 30).

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I encourage you to assum 90-x is the larger angle, and solve to prove to yourself that assumption is truly arbitrary.