Answer:
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.
Hope this helped
Let us convert the percentages to decimal format first.. so 5% is just 5/100 or 0.05 and 15% is just 15/100 or 0.15
so hmmm, so, let's say it needs "x" amount and "y" amount of each respectively, so, whatever "x" and "y" are, they must add up to 100, and whatever their concentration is, must add up to what the mixture yields
thus

solve for "x"
what's "y"? well, y = 100 - x
the answer is C, because you solve 2.815-749, and after you divide the result per 4, so it is 1/4
There is a higher chance that the dad is right because he is betting on a pretty much 50/50 chance while the mom is betting on a 25% chance