The answers:
2. When needing to find the slope of a line, or the rate of change
I’m not sure if your asking for the rise/run formula or the y=mx+b formula, so I’ll explain both and u can write the one your talking about
if your talking about the y=mx+b formula then here is the answer for number 3:
3. You use the slope formula by putting the slope in place of the m (in rise/run form)
if your talking about the rise/run formula, then ignore the last answer and use this answer for number 3:
3. You use the slope formula by counting how many units on the y axis the line goes up and then use it as the rise in rise/run. And then count how many units on the x axis the line goes sideways and use it as the run in rise/run