Supplementary angles add to equal 180 degrees. If two angles are supplementary and one angle measures 10x degrees and the other angle measures 60 degrees, you can set the sum of 10x and 60 equal to 180 and solve algebraically for x.
1) 180 = 10x + 60 : Add '-60' to each side of the equation.
60 + -60 + 10x = 180 + -60
2) Before you get to the simple part you need to do : 10x = 180 + -60
So, combine like terms : 180 + -60 = 120 10x = 120
3) Divide by 10 : 12 = 10x
4) Simplify it : 12 = x
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