What unknown number makes these equation true. 447+99 =447+100-

21

To find the unknown number that makes the equation true, let's break down the equation step by step.

The given equation is:
447 + 99 = 447 + 100 -

To solve this equation, we need to find the number that completes the equation after the subtraction symbol "-". Let's represent that unknown number with the variable "x".

Now, we can rewrite the equation as:
447 + 99 = 447 + 100 - x

To solve for "x", we need to isolate it on one side of the equation.
By subtracting 447 from both sides of the equation, we get:
447 + 99 - 447 = 447 + 100 - x - 447

Simplifying:
99 = 100 - x

Next, we can isolate "x" by subtracting 100 from both sides of the equation:
99 - 100 = -x

Simplifying further:
-1 = -x

To find the value of "x", we can multiply both sides of the equation by -1 (to remove the negative sign):
-1 * -1 = -x * -1

Simplifying:
1 = x

Hence, the unknown number that completes the equation is 1.