20.
60
(x + 20)
Зх
Sum of angle
measures: 180°

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Sum of the interior angles of any triangle equal 180° .
Thus ;
[tex](x + 20) + 3x + 60 = 180[/tex]
[tex]4x + 80 = 180[/tex]
Subtract sides 80
[tex]4x + 80 - 80 = 180 - 80[/tex]
[tex]4x = 100[/tex]
Divide sides by 4
[tex] \frac{4}{4} x = \frac{100}{4} \\ [/tex]
[tex]x = 25[/tex]
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