EF || AC ==》 180 - 4x = EBC ( ♡ )
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And also :
ABD = FBC ==》 FBC = x ( ☆ )
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EBC = EBF + FBC
( ♡ ) , ( ☆ ) :
180 - 4x = 65 + x
Subtract both sides 65
180 - 65 - 4x = 65 - 65 + x
115 - 4x = x
Add both sides 4x
115 - 4x + 4x = x + 4x
115 = 5x
Divide both sides by 5
115 ÷ 5 = 5x ÷ 5
23 = x
x = 23
And we're done ...