I'm assuming a 5-card hand being dealt from a standard 52-card deck, and that there are no wild cards.
A full house is made up of a 3-of-a-kind and a 2-pair, both of different values since a 5-of-a-kind is impossible without wild cards.
Suppose we fix both card values, say aces and 2s. We get a full house if we are dealt 2 aces and 3 2s, or 3 aces and 2 2s.
The number of ways of drawing 2 aces and 3 2s is

and the number of ways of drawing 3 aces and 2 2s is the same,

so that for any two card values involved, there are 2*24 = 48 ways of getting a full house.
Now, count how many ways there are of doing this for any two choices of card value. Of 13 possible values, we are picking 2, so the total number of ways of getting a full house for any 2 values is

The total number of hands that can be drawn is

Then the probability of getting a full house is

B) 1.339 x 10^6 gallons. When you add 812,000 to 527,000 you get 1,339,000, and to write that in scientific notation you need to make the number less than 10 and more than 1, which is 1.339 and to get the 1,339,000 you need to multiply 1.339 by 10^6.
Use PEMDAS. So it would then simplify to [100+(586+4)]/5<19 then continueing that it would be [100+590]/5<19 and then 690/5<19 which finally will be 138<19 and that is a valid statement