Question

What is the value of y when x = 3?

y = 12x

Answer 1

This is as simple as replacing the variable with the number.
y=12*3 Since X=3, we can replace x with 3 to actually do the question.
y=36 There is your answer!

Answer 2

y = 12x

Plug in 3 for 'x':

y = 12(3)

Multiply:

y = 36