p varies directly as q and p = 28 when q=7

Question

a.write an equation that relates p and q

b. find q when p=12

c. find p when q = 5

Answer 1

p = kq
when p = 28, q=7
28 = 7k
k = 4

so p = 4q

now you can find any variable if the other is known

e.g.
c) find p when q = 5
p = 4(5) = 20

you do the others.