-2x + 12 = 2y
Add 2x on both sides,
12 = 2y + 2x
Divide by 2 on both sides,
6 = y + x -> x + y = 6
The answer is D.
Class B has the most consistant sleep because there is less of a difference between 6.87 and 3.65 than the other classes.
(y-2)4 + 21
You subtract two because the 21 accounts for it and then whatever you have left multiplied by 4 and added to 21 is the amount of years after conversion.
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