Question

find the missing number in the proportion.
$\frac{5}{4} = \frac{x}{12}$

Explanation:

Step1: Cross - multiply the proportion

Given the proportion $\frac{5}{4}=\frac{x}{12}$, cross - multiplying (which is based on the property of proportions: if $\frac{a}{b}=\frac{c}{d}$, then $a\times d = b\times c$) gives us $4\times x=5\times12$.

Step2: Simplify the right - hand side

Calculate $5\times12 = 60$, so the equation becomes $4x = 60$.

Step3: Solve for x

Divide both sides of the equation $4x = 60$ by 4. That is $x=\frac{60}{4}$.
Simplify $\frac{60}{4}=15$.

Answer:

The missing number $x$ is 15.