Answer: -58
Explanation:
Start by looking for key words and numbers in your question/statement:
The sum of 18 and a number, x, equals negative 40.
Notice the word sum.
Sum is addition so x plus 18 is equal to -4.
Now that we have our equation (x+18=-40) we can solve by reversing the addition with subtraction:
X+18=-40
-18. -18
X=-58
Now that you know what X is equal to, check it by plugging it back into the equation.
-58+18=-40
It fits! So -58 is your answer.
Hope this helped;)