Question

The variables y and x have a proportional relationship, and y = 7 when x = 2.

What is the value of x when y = 21?

Answer 1

y is directly proportional to x
y=kx where k is a constant
7=2k
k=7/2
therefore, y=7/2x
21=7/2x
x=21×2/7
x=6