Answer:
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The sixth number should be 16 in order for the mean to be 12
1) From the data, we can see that

is given.
2) Next,

since they are alternate angles.
3) By substitution, these means that

4) Finally, a || b since

this is because, angle 7 and angle 8 are corresponding angles.
Corresponding angles are angles that are on the same corner at each intersection. For instance, 2 and 6
4 and 8, 1 and 5, 3 and 7
In our case, 7 and 8 are corresponding angles
You know the missing side of the bottom base is 6 because of the 30 60 90 special right triangle. The height is 6sqrt3 because of what i said above too, The area of a trapezoid is 1/2 b1+b2*h so 30+36*6sqrt3 is 396sqrt3 divided by 2 is 298sqrt3
<span>n/100 * 64 = 8 </span><span>n/100 = 8/64<span>
n = 8*100/64 = 25/2 = 12.5</span><span>
8 is 12.5% of 64 hope this helps:)</span></span>