She would have paid 1,575 dollars plus the 800 down payment. The total would be $2,375.
The requirement is that every element in the domain must be connected to one - and one only - element in the codomain.
A classic visualization consists of two sets, filled with dots. Each dot in the domain must be the start of an arrow, pointing to a dot in the codomain.
So, the two things can't can't happen is that you don't have any arrow starting from a point in the domain, i.e. the function is not defined for that element, or that multiple arrows start from the same points.
But as long as an arrow start from each element in the domain, you have a function. It may happen that two different arrow point to the same element in the codomain - that's ok, the relation is still a function, but it's not injective; or it can happen that some points in the codomain aren't pointed by any arrow - you still have a function, except it's not surjective.
I don't understand what your asking
Let n = the hours elapsed when the two trains are 660 miles apart.
Let the first train travel east and the second train travel west.
The distance traveled by the first train is
x = (50 mi/h)*(n h) = 50n mi
The distance traveled by the second train is
y = (60 mi/h)*(n h) = 60n h
The distance between the two trains after n hours is
x + y = 50 n + 60n = 110n mi
Because this distance is 660 miles, therefore
110n = 660
n = 6 hours
Answer: 6 hours
I hope this helps. Sorry it took so long
