Answer: 12 hours
Step-by-step explanation:
Given : Working together, it takes Sam, Jenna, and Francisco two hours to paint one room.
When Sam works alone, he can paint one room in 6 hours. When Jenna works alone, she can paint one room in 4 hours.
Let 't' be the time taken by Francisco to paint one room on his own.
Then , we have
Rate of work of Sam +Rate of work of Jenna + Rate of work of Francisco =Rate of work they all do together

i.e. 
i.e. 
i.e. 
i.e. 
i.e. 
i.e. 
i.e. t= 12
Hence, Francisco would take 12 hours to paint one room on his own.
This is true.
Example:
= 8/9 ÷ 7/3
to divide fractions, multiply by the reciprocal/inverse of 7/3
= 8/9 * 3/7
= (8*3)/(9*7)
multiply numerators; multiply denominators
= 24/63
simplify
= 8/21
ANSWER: This is (A) true
Hope this helps! :)
The wording of this question is a bit confusing... You can't write a sequence in sigma notation, but rather a series or sum. I think the question is asking you to write the sum of the sequence,

which would be

in sigma notation.
To do this, notice that the denominator in each term is a power of 2, starting with
and ending with
. So in sigma notation, this series is

The correct answer is B. Supplementary
That is the basic definition of what supplementary angles are and can be found in any textbook.