P is directly proportional to u.

Step-by-step explanation:

A direct proportion means the ratio of p:u is a constant numberThis constant number is denoted by kan example of this is, say for every 1 chicken you buy there are 2 legs which is ratio 1:2 which is so if you add more chickens, you add more legs, 2 chickens means 4 legs, 8 chickens means 16 legs, which is so the constant number is 0.5, so this a direct proportionThe two values grow at the same rate