The answer to 8a. is 17, the answer to 8b. is 3.9, the answer to 8c. is 1 / 2, the answer to 8d. is 7 7 / 8, the answer to 9a. is commutative property, the answer to 9b. is multiplicative identity property, the answer to 9c. is associative property, and the answer to 9d. is additive inverse property.
Regarding the whole "explain using mental math" thing, I pretty much just used the fact that 8a. and 8b. both had the same number of decimal places. For 8c., I just made each number have a denominator of 10. And last, for 8d., all of the denominators were already the same, which made it pretty easy. I apologize for this section of my answer being so informal lol, I haven't had to do these kinds of problems in like 5 years <span />
Answer:
There are 685464 ways of selecting the 5-card hand
Step-by-step explanation:
Since the hand has 5 cards and there should be at least 1 card for each suit, then there should be 3 suits that appear once in the hand, and one suit that apperas twice.
In order to create a possible hand, first we select the suit that will appear twice. There are 4 possibilities for this. For that suit, we select the 2 cards that appear with the respective suit. Since there are 13 cards for each suit, then we have 
possibilities. Then we pick one card of all remaining 3 suits. We have 13 ways to pick a card in each case.
This gives us a total of 4*78*13³ = 685464 possibilities to select the hand.
Of means multiply
3/5 *n=30
3/5 5/3 cancels than you do 30 *5/3 =50
The answer is 50 you can check your answer by doing 3/5 *50=150/5 or 30 so it's correct .
1/3 has the greatest value
