Working together, Bill and Tom painted a fence in 6 hours. Last year, Tom painted the fence by himself.
The year before, Bill painted it by himself, but took twice as long as Tom took. How long did Bill take
when painting the fence alone?

this is a kindergarten question.

6 times 2 is 12.

12 is the answer.

δabc ≅ δdcb by sas because

db ≅ ac . . given (side)

bc ≅ bc . . reflexive property (side)

∠dbc ≅ ∠ acb . . alternate interior angles where transversal bc crosses parallel lines bd and ac (included angle)

sample answer: you can determine whether each element of the domain is paired with exactly one element of the range. for example, if given a graph, you could use the vertical line test; if a vertical line intersects the graph more than once, then the relation that the graph represents is not a function.