Question 717745
The word "Sum" = addition. 
"A number" = the unknown, aka 'x'.
"Is equal to" is =.

Go piece by piece. I will set your equation exactly as it is worded as you read it. Follow along:

4x + (-2) = 5x + (-2)
Imagine there is a "1" infront of the parenthesis around the -2. A positive * a negative always = negative. So....

4x-2=5x-2
Get x alone on one side of the equation. I am going to chose to subtract 4x from the 5x. Resulting in:
-2 = x-2
X is still not alone. Now I will add the -2 to the other side, accomplishing x alone.
0=x or x=0

To check the answer, take the found value for x and plug it back into the original equation. Anything multiplied by 0 will equal 0. You are left with -2 =-2, which is true. 

:)