Question 889104
let y be the amount of cake mix 
let x be the number of people
k is the constant of proportionality
then we have the following equation
y = kx
a) 7 = k10
k = 7/10 = .7
y = .7x
b) y = .7 * 50 = 35 cups of cake mix
c) 12 = .7x
x = 12/.7 = 17.14 people