15÷x=2x÷120
15÷x=2x÷120
15÷x=2x÷120
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$15 : x = 2x : 120$
$x= \frac{15×120}{2x}$
$x= \frac{1800}{2x}$
$x×2x= 1800$
$2x^2 = 1800$
$x^2 = \frac{1800}{2}$
$x^2 = 900$
$\sqrt{x^2} = \sqrt{900}$
$x= ±30$
15/x = 2x/120
1800 = 2x^2
x^2 = 900
x = √900
x = ± 30