An Ap student got a lab report back with "-4.5 % error" written in red on it. He had found the boiling point of an unknown liquid to be 45 C. What is the correct boiling point of his unknown liquid?

I know first I would write -4.5 % error = |4.5-x|/x x 100 but I don't know what to do after that.

See your post above.

To determine the correct boiling point of the unknown liquid, we can start by setting up the equation you mentioned:

-4.5 % error = |4.5 - x| / x * 100

Let's break down the steps to solve for x, which represents the correct boiling point:

1. Rewrite the equation to remove the absolute value:
-4.5 = (4.5 - x) / x * 100

2. Simplify the right side of the equation:
-4.5 = (4.5 - x) / x * 100

Divide both sides of the equation by 100 to get rid of the fraction:
-0.045 = (4.5 - x) / x

Multiply both sides by x to eliminate the denominator:
-0.045x = 4.5 - x

3. Move all terms containing x to one side:
-0.045x + x = 4.5

Combine like terms:
0.955x = 4.5

4. Solve for x by dividing both sides of the equation by 0.955:
x = 4.5 / 0.955

5. Calculate the value of x:
x ≈ 4.71

Therefore, the correct boiling point of the unknown liquid would be approximately 4.71°C.