Answer: D . 
Step-by-step explanation:
Given : Jenny studied the characteristics of two species of bacteria. The number of bacteria of species A, A(t), after t hours is represented by the function,

The number of bacteria of species B, B(t), after t hours is represented by the function, 
Then, the difference in the number of bacteria, N(t), of both the species after t hours will be :-

Hence, the correct answer should be : D . 
To find how long it would take him, one has to divide 400 by 160 and then multiply 5 by what that number is. You multiply 5 by the quotient because that is the number that would make it proportional. 400/160 x 5 is 12.5, meaning that the answer is 12.5 minutes, or A.
Answer:
13
Step-by-step explanation:
7 cm +1 cm +2cm +2cm :12cm
11. The answer would be 3:30 because in all it took her 3:50 minutes so subtract from 7:20 you get 3:30