Answer:
x = 17
Explanation:
a straight line equals 180º so each side is 90º.
90 - 39 = 51
3 x __ = 51
3 x 17 = 51
so..x = 17
3x +39 =90
3x =90-39
3x=51
make it in fraction
3x over 3 equals to 51 over 3
simplify
= 51
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