2.25 x 10^-17. Because it's negative you move the decimal to the left. So 2.5 x 10^-8 is .000000025 and 9 x 10^-10 is .0000000009.
Your limting the amount of sandbags you have if you take away and when your adding your adding more sandbags.
The answer to the question is a
N(4)-1
n(4)-2
ex 2(4)=8
8-1=7
7(4)=28
28-2=26
so the next number would be 1595
If she took $20 out of her savings account, given the information, she could easily have no money remaining now. Given this, we'll assume the current value of her account is the minimum it can be. Now you just need to find how many times her withdrawal can factor into the original amount, $250. Therefore, t=250/20= 12.5. Since it's asking for a number of weeks, the answer can't be a decimal, so your final answer is 12 weeks.