Step-by-step explanation:
I'm going to assume you meant to write 
in the equation as +1 - 1 wouldn't make much sense since they would just cancel out.
a. 
b. 
c. 
The increase is D: 50% because the 1 in the parentheses stands for the 20 that was already there, with the .5 being the amount that’s actually being increased. 0.5 translates to 50%, so the answer is D.
Answer:
The first one
Step-by-step explanation:
To figure out which one is the best deal, for each one how much <em>one</em> t-shirt costs.
<u>First deal:</u>
3 t-shirts for $28.95
To figure out how much money one t-shirt would cost, you divide $28.95 by 3.
1 t-shirt = 28.95/3 = $9.65.
<u>Second deal:</u>
4 t-shirts for $39
Same thing as the last one, except since there are 4 t-shirts you divide $39 by 4.
1 t-shirt = 39/4 = $9.75
<u>Third deal:</u>
5 t-shirts for $49.95
This time you will divide 49.95 by 5.
1 t-shirt = 49.95/5 = $9.99
The last step is to compare the three deals, and since you are trying to find the one that costs the <em>least</em> you can see that the first deal is the best one, because $9.65 per shirt is cheaper than $9.75 and $9.99
