What is x is this equation (3x)/8 = (x+7)/12 ?

Jul 11, 2016

$x = 2$

Explanation:

Cross multiply ($\frac{a}{b} = \frac{c}{d}$ is the same as $a d = b c$).

$\frac{3 x}{8} = \frac{x + 7}{12}$

$3 x \left(12\right) = 8 \left(x + 7\right)$

$36 x = 8 x + 56$

$28 x = 56$

$x = 2$

Jul 16, 2016

$x = 2$

Explanation:

A method which works for solving any equation which has fractions, is to multiply by the LCM of the denominators.

This allows us to cancel the denominators which makes solving the equation much easier.

$\frac{3 x}{8} = \frac{x + 7}{12} \text{ LCM = 24}$

$\frac{24 \times 3 x}{8} = \frac{24 \times \left(x + 7\right)}{12}$

$\frac{{\cancel{24}}^{3} \times 3 x}{\cancel{8}} = \frac{{\cancel{24}}^{2} \times \left(x + 7\right)}{\cancel{12}}$

$9 x = 2 \left(x + 7\right)$

$9 x = 2 x + 14$

$7 x = 14$

$x = 2$