Answer: There are 20 boys
Step-by-step explanation:
Answer:
The alternative hypothesis is
.
The critical value is 
Step-by-step explanation:
It is claimed that proportion in favor of proportion A is greater than 60%.
This means that at the null hypothesis, we test if the proportion is of at most 60%, that is:

At the alternative hypothesis, we test if the proportion is more than 60%, that is:

What is (are) the critical value?
The critical value is the value of Z with a p-value 1 subtracted by the standard significance level of 0.05, since we are testing if the mean is more than a value, so, looking at the z-table, 
Answer:
Step-by-step explanation:
|2(-5) - 1| + 10
|-10-1| + 10
|-11| + 10
11 + 10
21 is your answer
Hope this helped!