Answer:
She made a mistake in Step 7.
Step-by-step explanation:
Step 1 through 6 are correct. Only from Step 6 to Step 7 the problem comes in: both sides of the equation are multiplied by x, however the x on the left side, by error, becomes 1. The correct state in Step 7 should look like this:

Well they give you the equation and they want you to solve for time given that you know the amount of water in the tank. They tell you T=274 and that
T=450-8m so using the value T=274 in the equation to the left gives you:
274=450-8m subtract 450 from both sides
-176=-8m divide both sides by -8
22=m
So 22 minutes have passed when there is 274L remaining...
Answer:
7
Step-by-step explanation:
A squared plus B squared equals C squared, so what you need to do it square 5 and 7.
5 = 25
7 = 48
Then add then and square root your answer. 48 + 25 = 73. 73 square rooted equals an rounded amount of 8.6. SO the answer is D