Answer:
7.5
Step-by-step explanation:

<span>A+B)^2 is the largest. It is A^2+2AB+B^2, which is clearly greater than the last two options. To compare (A+B)^2 and 2(A+B), we remove one A+B so that we're just comparing A+B and 2. As A+B must be at least 3 (as both must be positive integers, and one must be greater than the other, leading to a minimum value of A=2, B=1), A+B is greater than 2, and as a result, (A+B)^2 is always the largest.</span>
D....the empty weight is 160gr
-0.272727272727272727272727272727
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!