Answer:
0.75
Step-by-step explanation:
Using the equation
y=mx
where y is the cost, m is constant and x is variable representing packages
8.85=15x
5.1=10x
Subtracting equation 2 from 1 then
5x=3.75
x=3.75/5=0.75
x=0.75
The constant of proportionality is 0.75
