Whats the queastion think
For this case, the first thing we must do is define variables.
We have then:
x: number of minutes
y: final temperature
We write then the equation that models the problem:

For y = 20 we have:

Clearing x:
Answer:
The temperature of the water will be 20 degree celcius after 150 minutes
Its A or 6 because 30 divided by 5 is 6