With any parallelogram, the diagonals bisect each other. This is another way of saying that they cut each other in half.
FH is one diagonal that is split into two equal pieces by the other diagonal EG.
The two parts of FH (KH and KF) are congruent to each other, so KH = KF. They combine back to FH
By the segment addition postulate
KH + KF = FH
KH + KH = FH .... KF has been replaced with KH (works because KF = KH)
2*KH = FH
Now use substitution
2*KH = FH
2*15 = FH .... replace KH with 15 (since KH = 15)
2*15 = 4x-2 ... replace FH with 4x-2 (since FH = 4x-2)
and solve for x
2*15 = 4x-2
30 = 4x-2
30+2 = 4x-2+2 ... add 2 to both sides
32 = 4x
4x = 32
4x/4 = 32/4 ... divide both sides by 4
x = 8
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Answer: x = 8
Rectangular Prism
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The proportion is 0.4401.
We find z-scores that correspond with both ends of this interval. Z-scores are given using the formula:

For the lower end,

The proportion of scores to the left of this number is 0.2514.
For the higher end, the z-score is

The proportion of scores to the left of this number is 0.6915.
To find just the proportion of scores between these two, we subtract;
0.6915-0.2514 = 0.4401.
About 20.7 minutes you get to spend with each dog for a total of 145 minutes.