First, lets assign a letter to each angle:
a = smallest angle
b = largest angle
c = 3rd angle
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The question tells us the following:

Therefore:

We are also told:

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Now lets form three equations by swapping out the angles with the correlating letter:



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Remember, angles in a triangle add up to 180, so we can make another equation:

Now substitute in the values in terms of a, for b and c - and then solve for a. (to solve the equation, everything has to be in the same terms, which is a in this case):




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Now that we know what a is, we can work out what b and c is, by substituting in the value of a into their equations:
Value for b:



Value for c:



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a = smallest angle
b = largest angle
c = 3rd angle
So:
30 = smallest angle
90 = largest angle
60 = 3rd angle
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Answers:
The measure of the angles from smallest to biggest are:
30°,
60°, and
90°
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