<h2>D. If subjects knew they were receiving an active treatment, researchers would not have known if any improvement was due to the new medication or to the expectation of <u>feeling </u>better. If the researchers knew which subjects received which treatments, they might have treated one group of subjects differently from the other group.</h2><h2 />
For your question... the answer would be D
The rate a computer works is 1/time. Working together, you add the rates.
Let new computer be x, old computer be y.
x = y - 7

Rounded to nearest tenth gives:
x = 23 hours
Answer:
x = 4
Step-by-step explanation:
4(5x - 2) = 72
Do the distributive property
20x - 8 = 72
Then add 8 to both sides to get 20x alone
20x - 8 = 72
+ 8 + 8
20x = 80
Then divide both sides by 20 to get x

x = 4
It will travel 180 miles
4.5 • 40= 180