Answer:
91 used
65 new
Step-by-step explanation:
7 + 5 = 12
156/12 = 13
7(13) = 91
5(13) = 65
Use distribution
-5t - 30 + 7t = 100
Combine like terms
2t - 30 = 100
Add 30 to both sides
2t = 130, t = 65
Solution: t = 65
Multiplication and division with the powers of ten
So, when multiply powers of ten, all you have to do add up the powers.
The reverse goes when you are dividing. You would subtract the powers.
9 x 10^7 => 3 x 10^3
The words " how many times as large as " indicates that we are going to divide the two, making it look like this:

Divide the 9 by 3 you get 3
Then subtract 10^3 from 10^7
Therefore, the answer is 3 x 10^4, or A