1. Sara bought cartons of raspberries that cost $1.50 and cartons of blackberries cost $2. Sara spent $11 buying raspberries and blackberries. She bought a total of 6 cartons. How many cartons of blackberries did she buy?

Sara brought a total of 5 cartons of blackberries. Since it said that Sara brought 6 cartons and you know that the cost of the blackberries are $2, you multiply 6 with 2 but its 12. But if Sara  brought 2 cartons of raspberries it will be $3. Now you subtract 6 with 2 since you used 2 cartons on raspberries and now multiply $2 with 4 and get 8. 8+3=11, which is exactly how much she needs. This means that Sara brought 4 cartons of blackberries.

e^-kt = n/n0 = 0.79  

-kt = ln 0.79  

t = - ln 0.79/0.0001  

= 2357 years

step-by-step explanation: