We first want to know how many fl oz there are in one pint, there are 16. Let's use a proportion to solve this
x 9
16 fl oz n
--------- = --------
1 pint 9 pints
x 9
To get from 1 to 9, we multiply by 9. So we must do the same thing to 16, multiply by 9. 16 x 9 = 144. Therefore there are 144 fl oz in 9 pints.