\(\frac{9+x}{13-x}=\frac{5}{6}\)
<=> (9+x).6 = (13 - x).5
<=> 54 + 6x = 65 - x.5
<=> 11x = 65 - 54
<=> x = 11 : 11
<=> x = 1
\(\frac{9+x}{13-x}=\frac{5}{6}\)
=> 6(9 + x) = 5(13 - x)
=> 54 + 6x = 65 - 5x
=> 54 - 65 = - 5x + 6x
=> - 9 = - 1x
=> x = 9
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