The mistake she made was timesing the 6 by the -7.5 as there is no x after the 6
Therefore:
-3.8(-7.5) +6
28.5+6 =34.5
Question # 17 Solution
Answer:

Step-by-step Explanation:
The given expression

And we have to solve for x₁
So,
Lets solve for x₁.

Multiply both sides by x₂ - x₁




Divide both sides by -m


Therefore, 
Question # 23 Solution
Answer:

Step-by-step Explanation:
The given expression

And we have to solve for n
So,
Let's solve for n.

Multiply both sides by b.

Factor out n.

Divide both sides by -b + x.


Therefore, 
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sorry i dont have answered
Answer:
$7.22 or $7.217
Step-by-step explanation:
$7.22 would be the answer because 70% of 10.31 is what you are looking for which is 7.217 which is rounded to 7.22