Question 49398
If W is the midpoint of the line RS, it's basically saying W is exactly halfway between point R and point S.  If given R and S we can simply add the R and S points together and divide by 2.
 4+ (-6)=-2.......-2/2 =-1 so W=-1

In picture form, one dot will equal 1 number to proove the equation
-6....-1....4, notice there are 4 dots between R and W and 4 dots between S and W.


When either R or S is not given, the same formula can be applied but now algebra is used....or counting, your choice.

(R+S)/2=W
(R+2)/2=-4.....R+2=-8......R=-10, this can also be prooved by the number line
-10.....-4.....2, there are 5 numbers between each R and W and S and W

Hope this helps