ok, think about it this way, the constant of proportionality is pretty much how y and x are related, say r is the constant of proportionality, then your answer would ne y = rx
so the constant of proportionality for your question would be 2.5 since you had y = 2.5x
There is a total of 5 colors. The probability of landing on orange can be represented as 1(orange): 5(total). This answer can also be represented as 20%. To make 1:5 a percentage you divide 1 by 5, then multiply it by 100.