From past experience, a professor knows that the test scores of a student taking the final exam is a random variable with mean 75 and the variance is 16. How many students would have to take the exam to ensure with probability 0.9 that the class average would be within 5 of 75

Justifying my reasoning, using the angle addition postulate, 20 + m∠dbc = 80. so, m∠dbc = 60° using the subtraction property of equality. So, m∠dbc = 100° using the addition property of equality.

Step-by-step explanation:

a) using the angle addition postulate, 20 + m < dbc = 80. so, m < dbc = 60° using the subtraction property of equality.

b) using the angle addition postulate, 20 + 80 = m < dbc. so, m < dbc = 100° using the addition property of equality.

c) using the addition property of equality, 20 + 80 = 100, so m < dbc = 100°.

d) using the subtraction property of equality, 80 - 20 = 60, so m < dbc = 60°