Pls me asap for (must show ) + lots of

If the rate at which the temperature fell is 4/5 degree/hour then we can simply multiply 5 hours to get our answer. 

4/5 * 5/1 = 20/5 = 4

So, it would change a total of 4 degrees.

I hope this helps. If something is confusing or this answer is wrong, don't be afraid to drop me a DM telling me what is wrong.

What you have to do is this: multiply the number of hours by how much the temperature changes each hour.
So this is what you get: 4/5 * 5, which is 4.