In these problems, you will try to find the missing number.

The missing number is called a variable and is usually shown as a letter like x or y.

4 + x = 5

Answer: x = 1

You can check if you are right by plugging back in your answer to the original equation:
4 + 1 = 5

To solve for the unknown number, you will try to get the variable on one side of the equal sign and all the numbers on the other side.

Whatever you do to one side of the equation you have to do to the other.

4 + x = 5

To get x on one side of the equal and the numbers on the other side, we will move the 4 to the right-hand side of the equation.

We will do that by subtracting it from the left side.

4 + x -4 = 5

The 4s will cancel out on the left side equaling zero. Because we subtracted 4 from the left side we must also subtract 4 from the right side.

x = 5 - 4

Now you just do the simple math.

x = 1