In this problem, we need to use the concept of proportions. Proportion says that two ratios (or fractions) are equal. So, we have two numbers, namely:
[tex] x=8 \ and \ y=20 [/tex]
So, the given proportion is:
[tex] \frac{x}{y}=\frac{8}{20} \\ \\ \therefore \frac{x}{y}=\frac{2}{5} [/tex]
That is, x-out-of-y is equal to 2-out-of-5
On the other hand, we know that [tex]x=42[/tex], so by using the previous proportion we have:
[tex] \frac{42}{y}=\frac{2}{5} \\ \\ Isolating \ y: \\ \\ y=\frac{42 \times 5}{2} \\ \\ y=\boxed{105} [/tex]
