Anything withdrawn you subtract. Then, you know the total and you know what you had. Subtract total from what you had and you will see the change.
1735.97-100=1635.97
1668.71-1635.97=32.74
Mono means one..but monomial can also a negative. Mono meaning one means there is a single variable.
The students will earn $180 by washing cars for 9 hours.
In 3 hours the students will earn...
$5 x 12 = $60
5 dollars x 12 cars = 60 dollars
So in 3 hours the group of students will earn $60
In 9 hours the students will earn...
$60 x 3 = $180
Since the students will earn $60 per every 3 hours, you multiply $60 with 3 because if you divide 9 hours by 3 hours you will get 3. The answer you get by multiplying 60 by 3 is 180. Therefore the students can earn $180 from washing cars.
I hope this helps!
Can you try rewording this question?