-18.2 + 3.6= -14.6 is the answer to the question
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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Answer:
21
first we begin from 1 to 100 we find 11 numbers contain 1 then we count 1s from 10 to 19 we get 9 numbers but there is an exciption in number 11 as it cotains 2 1s so thenumber of 1s is 21