Total up the Consumption,Investment, Government Spending and Exports then minus the Total Imports. So the correct answer is C. $4,100
Times as many means multiply
hope this helps
Use the sum of cubes factoring rule

to transform the left hand side into the right hand side.


Throughout the entire process, the right hand side stayed the same.
On the last step, I used the pythagorean identity.
If they are growing 80% for every twodays, it would be 40% for every one day.
Bacteria after 9 days = 212 * 9 * 40 / 100
= 763.2
To round up, the population of bacteria after 9 days would be 763, with a growth rate of 80% for every two days.