B because if you simplify 9/15 by 3 you have 3/5
Perhaps I don't understand the question. You only need to choose one pair that adds to 16, any of {1, 15}, {3, 13}, {5, 11}, {7, 9}.
You can choose up to 4 numbers without getting a pair that adds to 16, so if you choose any 5 numbers, at least one pair of them will add to 16.
Thirty over eighty and six over eighteen
A simple rule to tell whether a graph is a function is to pretend to cut it vertically, if any cut intercept the graph twice, it is not a function. otherwise, it is.
In this case, the heart is not a function, because if you cut it up-down direction, your imaginary knife will touch the edge of the heart twice.
I hope this explanation helps.<span />
