1) A={3,5,7,9,11} B={4,8,12}, and A∪B ={3,4,7,8,9,11,12}
2) Normal distribution with Mean 80% & SD = 5%
The here below "distribution" is easy to figure out
--70%----------75%------------ 80%--------85%-----90%------
-2σ -1σ Mean 1σ 2σ
You should know for + or - 2σ the probability is 95%. Since here we are taking half of it will be 47.5%
For the last one I don't have the Z-Score Table. Sorry
