The "m" in y = mx + b is the <u>slope.</u>
It is the number of units a point goes up, down, left, or right each time. Making the line linear/straight.
"rise" is the the number of units you go up(+) or down(-), "run" is the number of units you go to the right
For example, if your slope is:
You are going up 1 unit, and to the right 2 units
3 or 
You are going up 3 units, and to the right 1 unit
You are going down one unit, and to the right 2 units
-3 or 
You are going down 3 units, and to the right 1 unit
The electric field strength at any point from a charged particle is given by E = kq/r^2 and we can use this to calculate the field strength of the two fields individually at the midpoint.
The field strength at midway (r = 0.171/2 = 0.0885 m) for particle 1 is E = (8.99x10^9)(-1* 10^-7)/(0.0885)^2 = -7.041 N/C and the field strength at midway for particle 2 is E = (8.99x10^9)(5.98* 10^-7)/(0.0935)^2 = <span>-7.041 N/C
</span>
Note the sign of the field for particle 1 is negative so this is attractive for a test charge whereas for particle 2 it is positive therefore their equal magnitudes will add to give the magnitude of the net field, 2*<span>7.041 N/C </span>= 14.082 N/C
X(m+n) = p
x = p/(m+n)
Hope this helps!
For a problem 1 the answer is 3×6+6×9.
for a problem 3 the answer is 9×10+8×7
for problem 4 the answer is 4×8+8×4+8×4.
