Answer:
a) 
b)
Step-by-step explanation:
Data
Brine a (Ba)

Brine b (Bb)

we have that per every minute the amount of solution that enters the tank is the same as the one that leaves the tank (15 Lt / min)
, then the amount of salt (y) left in the tank after (t) minutes: 
Finally:
a) 
b) 
being y(t) the amount of salt (y) per unit of time (t)
90k/60minutes, the car travels 3/2 kilometers in a minute. 20 x 3/2 is 30 kilometers that the car travels in 20 minutes.
Answer:
Hello!
Step-by-step explanation: