Go over 9x and that should be it
Answer:
They can either decrease the confidence level or increase the sample size, that is, survey more students.
Step-by-step explanation:
The width of a confidence interval is given by:

In which z is the critical value correponding to the confidence level(higher confidence level, higher z is),
is the standard deviation of the population and n is the size of the sample.
The students realize that this interval contains a large margin of error. What can they do to make a narrower interval?
Looking at the formula for M, they can either decrease the confidence level or increase the sample size, that is, survey more students.
Sin Q = oppo. / hypo
sin Q = 9/15
sin Q = 0.6
MCE = 360 - (150 + 70 + 50)
mCE = 360 - 270
mCE = 90
<CDE = 1/2(mBE + mCE)
<CDE = 1/2(150 + 90)
<CDE = 1/2(240)
<CDE = 120
answer
<CDE = 120°