we are given
number of pretzels =y=7
number of people=x=20
now, we have to find
constant of proportionality relates the number of pretzels to people
Let's assume they are directly related
so, we can use formula

where
k is constant of proportionality
y is number of pretzels
x is number of people
so, we can plug values
and we get

so, constant of proportionality is
...........Answer