Create proportions to do this question
When x is 8, y is 20
when x is 42, y is ?
\(\frac{8}{20}\) = \(\frac{42}{?}\)
Do cross multiplication:
8 × ? = 20 × 42
8 × ? = 840
Divide by 8 to isolate the unknown
\(\frac{8*?}{8}\) = \(\frac{840}{8}\)
8 and 8 cancels out
? = 105
y is 105 when x is 42
