It would be more difficult to run up a slope of 5 because it would be steeper. with a 1/5 slope you would have a rise over run but with a slope of 5 it would just be all rise
X*y=72
x = 5y-2
x=72/y
72/y=5y-2
72=5y^2-2y
5y^2 -2y - 72 = 0
(5y+18)(y-4)=0
y = -18/5 discard
or y = 4
4x=72
x=18
(18,4)
So :

?
First, you want to bring everything together on the top of the fraction.
12=24/2 so you can have

Add like terms -- 12 +24 = 36

Now we are at

Which is the lowest possible simplified version while remaining at exact value.
Feel free to check my math! I kinda did this off the top of my head.
Answer:
0.6 °C/min
Step-by-step explanation:
The relationship between rates and movement is ...
time = distance/speed
Here, the "distance" is measured in °C, and the "speed" is the rate of change of temperature.
For the first half of the heating, the time required is ...
(50°C -0°C)/(1.5 °C/min) = 50/(3/2) min = 100/3 min
For the second half of the heating, the time required is ...
(100°C -50°C)/(4/10 °C/min) = 50/(4/10) = 125 min
Then the total time is ...
((100/3) +125) min = (475/3) min
And the average rate of temperature increase is ...
total temperature change / total time
= (100°C -0°C)/(475/3 min) = 300/475 °C/min = 12/19 °C/min ≈ 0.6 °C/min