Give the age development from 4 to 9 months​

Of four agents alpha, beta, gamma anddelta, three have to be sent together on amission. if alpha and beta cannot gotogether, beta and gamma cannot go togetherand gamma and delta cannot go together,then which of the following holds? 1. any three agents can be sent.2. alpha, delta and any one out of beta andv gamma can be sent.3. beta, gamma and any one out of alphaand delta can be sent.4. the mission is impossible.

How do you work out 21.3-8= show your working. plz

Jerrold has to buy 12 copies of a textbook which costs $36.25 per copy. how much must he spend for them?