Question

Solve for x : 7/8 = 21/x

Answer 1

Hey!

We could write the problem like this,
$\frac{7}{8}=\frac{21}{x}$
Cross multiply!
$7x=8\cdot \:21$
We know that $8\cdot \:21=168$, let's plug that in.
$7x=168$
Divide both sides by 7.
$\frac{7x}{7}=\frac{168}{7}$

Our final answer would be,
$x=24$

Thanks!
-TetraFish

Answer 2

$\frac{21}{1} \frac{7}{8} = \frac{21}{x} ( \frac{21}{1} ) \\ Cross-out, the DOUBLE 21's \\ 7(x) = 21 \\ 21(8) = ? \\ 7(x) = 168 \\ \frac{168}{7} = 24 \\ Answer: x = 24$ $Choice. 2$