Answer: a) Required minimum sample size= 219
b) Required minimum sample size= 271
Step-by-step explanation:
As per given , we have
Margin of error : E= 5% =0.05
Critical z-value for 90% confidence interval : 
a) Prior estimate of true proportion: p=28%=0.28
Formula to find the sample size :-

Required minimum sample size= 219
b) If no estimate of true proportion is given , then we assume p= 0.5
Formula to find the sample size :-

Required minimum sample size= 271
I think you meant a+5(b)+c the answer is b is a unknown value
Answer:
Step-by-step explanation:
2x+3x+5x = 180°
x = 18°
Angles: 36°, 54°, 90°
Expand by multiplying out:
14-15t + 36 = 1 -20t -1,
Because of the minus before the bracket, it changes the sign inside the bracket
-15t + 20t = 1-1-14-36 Rearranging the ts on one side and the numbers on other
side.
5t = -50 Divide both sides by 5.
t = -50/5
t = -10.