check the picture below on the top side.
we know that x = 4 = b, therefore, using the 30-60-90 rule, h = 4√3, and DC = 4+8+4 = 16.
![\bf \textit{area of a trapezoid}\\\\ A=\cfrac{h(a+b)}{2}~~ \begin{cases} a,b=\stackrel{bases}{parallel~sides}\\ h=height\\[-0.5em] \hrulefill\\ a=8\\ b=\stackrel{DC}{16}\\ h=4\sqrt{3} \end{cases}\implies A=\cfrac{4\sqrt{3}(8+16)}{2} \\\\\\ A=2\sqrt{3}(24)\implies \boxed{A=48\sqrt{3}}](https://tex.z-dn.net/?f=%5Cbf%20%5Ctextit%7Barea%20of%20a%20trapezoid%7D%5C%5C%5C%5C%0AA%3D%5Ccfrac%7Bh%28a%2Bb%29%7D%7B2%7D~~%0A%5Cbegin%7Bcases%7D%0Aa%2Cb%3D%5Cstackrel%7Bbases%7D%7Bparallel~sides%7D%5C%5C%0Ah%3Dheight%5C%5C%5B-0.5em%5D%0A%5Chrulefill%5C%5C%0Aa%3D8%5C%5C%0Ab%3D%5Cstackrel%7BDC%7D%7B16%7D%5C%5C%0Ah%3D4%5Csqrt%7B3%7D%0A%5Cend%7Bcases%7D%5Cimplies%20A%3D%5Ccfrac%7B4%5Csqrt%7B3%7D%288%2B16%29%7D%7B2%7D%0A%5C%5C%5C%5C%5C%5C%0AA%3D2%5Csqrt%7B3%7D%2824%29%5Cimplies%20%5Cboxed%7BA%3D48%5Csqrt%7B3%7D%7D)
now, check the picture below on the bottom side.
since we know x = 9, then b = 9, therefore DC = 9+6+9 = 24, and h = b = 9.
![\bf \textit{area of a trapezoid}\\\\ A=\cfrac{h(a+b)}{2}~~ \begin{cases} a,b=\stackrel{bases}{parallel~sides}\\ h=height\\[-0.5em] \hrulefill\\ a=6\\ b=\stackrel{DC}{24}\\ h=9 \end{cases}\implies A=\cfrac{9(6+24)}{2} \\\\\\ A=\cfrac{9(30)}{2}\implies \boxed{A=135}](https://tex.z-dn.net/?f=%5Cbf%20%5Ctextit%7Barea%20of%20a%20trapezoid%7D%5C%5C%5C%5C%0AA%3D%5Ccfrac%7Bh%28a%2Bb%29%7D%7B2%7D~~%0A%5Cbegin%7Bcases%7D%0Aa%2Cb%3D%5Cstackrel%7Bbases%7D%7Bparallel~sides%7D%5C%5C%0Ah%3Dheight%5C%5C%5B-0.5em%5D%0A%5Chrulefill%5C%5C%0Aa%3D6%5C%5C%0Ab%3D%5Cstackrel%7BDC%7D%7B24%7D%5C%5C%0Ah%3D9%0A%5Cend%7Bcases%7D%5Cimplies%20A%3D%5Ccfrac%7B9%286%2B24%29%7D%7B2%7D%0A%5C%5C%5C%5C%5C%5C%0AA%3D%5Ccfrac%7B9%2830%29%7D%7B2%7D%5Cimplies%20%5Cboxed%7BA%3D135%7D)
Answer:
history test
Step-by-step explanation:
Problems of normally distributed samples can be solved using the z-score formula.
In a set with mean
and standard deviation
, the zscore of a measure X is given by:

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
In this problem, we have that:
He did better relative to the class in the test in which he had a higher Z score.
So:
History
Raul received a score of 75 on a history test for which the class mean was 70 with a standard deviation of 7. So we have 
So:



Biology
He received a score of 73 on a biology test for which the class mean was 70 with standard deviation 7. So we have 
So:



He had a higher Z score in the history test, so this is the test in which he did better relative to the rest of the class.
Hint: try our various values of a and b as integers, both positive and negative.