Since this is a proportion, we cross multiply.
12/2=9/x (The variable "x" is used the represent the unknown number, and this is the number we are solving for)
12*x=2*9 (Cross multiply)
12x=18 (Simplify)
x=18/12 (Divide each side by 12)
x = 3/2 (Simplify fraction)
The unknown number is 3/2, or 1.5.
