Can anyone me? my teacher just recently taught me this today, be he never explained much. the question is in the photo

You've got five different problems in this photo ... four on top and the word problem on the bottom ... and they're all exactly the same thing:  Taking two points and finding the slope of the line that goes through them.

In every case, the procedure is the same.
If the two points are  (x₁ , y₁)  and  (x₂ , y₂) , then
the slope of the line that goes through them is

                          Slope  =  (y₂ - y₁) / (x₂ - x₁) .

This is important, and you should memorize it.

#1).  (8, 10)  and  (-7, 14)

         Slope  =  (14 - 10) / (-7 - 8)  =  4 / -15

#2).  (-3, 1)  and  (-17, 2)

         Slope  =  (2 - 1) / (-17 -  -3)  =  (2 - 1) / (-17 + 3)  =  1 / -14

#3).  (-20, -4)  and  (-12, -10)

         Slope  =  [ -10 - (-4) ] / [ -12 - (-20) ]



The word problem:

This question only gives you one point on the graph,
and then it wants to know what's the slope ?
What are you going to do for another point ?

A "proportional relationship" always passes through the origin,
so another point on the line is  (0, 0) .

Now you have two points on THAT line too, and you can easily
find its slope.

You just divide and you will find x