Answer:

Step-by-step explanation:
Let x = number of books that Hannah donated
We know that the number of students is 150 and the total number of books is represented by b, we can write that as:
Average number of books donated by each student = 
Now we know that Hannah donated 3 times as much as the average. We can write that as:

For this case we must find the surface area of a rectangular prism.
We have then:

Where,
w: width
l: long
h: height
Substituting values we have:
Answer:
There will be needed 88 in ^ 2 of giftwrap to cover the box
You have two 30-60-90 triangles, ADC and BDC.
The ratio of the lengths of the sides of a 30-60-90 triangle is
short leg : long leg : hypotenuse
1 : sqrt(3) : 2
Using triangle ADC, we can find length AC.
Using triangle BDC, we can find length BC.
Then AB = AC - BC
First, we find length AC.
Look at triangle ACD.
DC is the short leg opposite the 30-deg angle.
DC = 10sqrt(3)
AC = sqrt(3) * 10sqrt(3) = 3 * 10 = 30
Now, we find length BC.
Look at triangle BCD.
For triangle BCD, the long leg is DC and the short leg is BC.
BC = 10sqrt(3)/sqrt(3) = 10
AB = AC - BC = 30 - 10 = 20
If you would like to know what was the percent decrease in price, you can calculate this using the following steps:
x% of $299.99 is $180.55
x% * 299.99 = 180.55
x/100 * 299.99 = 180.55
x = 180.55 * 100 / 299.99
x = 60.19%
100% - 60.19% = 39.81%
The correct result would be 39.81%.