the easiest way to do this is by setting up a proportion, so
180 per every 12 hours of work = 180/12
and you want to know how much she would make for only 9 hours
(180 dollars/12 hours) = (x dollars/9 hours)
9 belongs on the bottom of your second fraction because you want it to be in the same place
from there you just solve the proportion; 180 divided by 12 is 15
15 = x dollars/9 hours
multiply both sides by 9
x = 135 dollars
so kira makes $135 in 9 hours of work