Start writing the proportion as a fraction
[tex]\begin{gathered} 4\colon7\rightarrow\frac{4}{7} \\ x\colon5\rightarrow\frac{x}{5} \end{gathered}[/tex]
then, the ratios must be the same meaning we can equal the fractions
[tex]\begin{gathered} \frac{4}{7}=\frac{x}{5} \\ \text{cross-multiply and solve for x } \\ x=4\cdot\frac{5}{7} \\ x=\frac{20}{7} \end{gathered}[/tex]
repeat the same procedure for b
[tex]\begin{gathered} x\colon8\rightarrow\frac{x}{8} \\ 99\colon5\rightarrow\frac{99}{5} \\ \text{then,} \\ \frac{x}{8}=\frac{99}{5} \\ x=8\cdot\frac{99}{5} \\ x=\frac{792}{5} \end{gathered}[/tex]
