To find this answer, you must first find out how much each car makes them. You do 144 divided by 24 to do this. You get the answer 6. Which means that they make $6 for each car washed.
Now that you know how much each car wash makes them, you multiply 6 by 30 to get how much they earned on Sunday.
6 x 30= 180.
So, they earned B.$180 on Sunday