Explanation:
the solution of an equation for a variable (here x) means that we transform the equation via arithmetic operations (always on both sides of the equation) until we get it into a form
x = ...
so,
5x - 10 = -40
first I suggest we eliminate the additional -10 on the side with the variable by adding 10 to both sides :
5x - 10 + 10 = -40 + 10
5x = -30
and now we eliminate the factor of 5 from our variable by dividing both sides by 5 :
5x/5 = -30/5
x = -6
and that was it. that was all that was needed.