Question 48117
10/15*(100-75)=(2/3)*25=16.67
75-16.67=58.33

suppose y is the temperature of the water in the kettle,
x is the amount of time after the water was boiled.
So y=100-25(x/15), but the water will stay at room temperature and cease to decrease so when y=20, x=((100-20)/25)*15=(16/5)*15=48
The line on the graph change directions after x=48
1)48>=x>=0, y=100-25(x/15)
2)x>=48, y=20