How do you find the proportionality ?

Proportions can sort of act like ratios. I would solve it like a chart. $2 for 4 oranges. $3 for 6 oranges. That shows numbers in a proportion or a group. The base ratio is $1 for 2 oranges. Ratios can be fractions too. If you multiply 2 to the $1 to make it $2, the number of oranges you get increases too. Hope this helps!