120 gallons in 4 days.....120/4 = 30 gallons per day
for 28 days...
30 * 28 = 840 gallons <==
Now go to school...lol
1. X+7=21
-7 -7
X=14
2. X-5=13
+5 +5
X=18
3. 4x=48
— —
4 4
X=12
4. 7(X/7)=(15)7
X=105
The area of a trapezoid is

where B and b are the two bases, and h is the height. The two bases have to be parallel, and the height must be perpendicular to both bases.
Even though we are used to have horizontal bases and vertical height, it's not mandatory, since a simple rotation doesn't affect the dimensions or the area of the trapezoid.
So, in this case, the two vertical segments are actually the bases of the trapezoid, and the horizontal segment is the height. So, the formula for the area yields

We would have the following sample space:
(1, 1), (1, 2), (1, 3), (1, 4)
(2, 1), (2, 2), (2, 3), (2, 4)
(3, 1), (3, 2), (3, 3), (3, 4)
(4, 1), (4, 2), (4, 3), (4, 4)
Those give us these sums:
2, 3, 4, 5
3, 4, 5, 6
4, 5, 6, 7
5, 6, 7, 8
P(sum of 2) = 1/16 =0.0625
P(sum of 3) = 2/16 = 0.125
P(sum of 4) = 3/16 = 0.1875
P(sum of 5) = 4/16 = 0.25
P(sum of 6) = 3/16 = 0.1875
P(sum of 7) = 2/16 = 0.125
P(sum of 8) = 1/16 = 0.0625