Set up the ratios as proportional fractions:
[tex]\frac{12}{15} = \frac{x}{5}[/tex]
We can simplify the first fraction to make the problem easier. Both the numerator and denominator of the first fraction can be divided by 3:
[tex]\frac{12}{15} \div \frac{3}{3} = \frac{4}{5}[/tex]
[tex]\frac{4}{5} = \frac{x}{5}[/tex]
Both fractions now have the same denominator. Since both fractions have to equal each other, the numerators will also be the same. Therefore, x = 4.
