The probability for event a is 0.4 the probability for event be is 0.2 and the probability of events A and b is 0.1 why are the events are not independent

Trent wants to buy 2 packs of trading cards for 3 dollars each. the trading card packs that trent normally buys tend to come in packs of 6, 10, 12, or 15 cards. after selecting 2 packs, trent found that the first pack of cards cost 25 cents per card, and the second pack cost 30 cents per card. trent uses this information to write the equations below in order to compare c, the number of cards in each pack.

Can anyone me get through my algebra 2 class? the only class i need to graduate..

Find the value of x. also give me an explanation so i can complete it to other questions as well, : )