The directrix of the parabolas are parallel to the x-axis.
This means that, the orientation of the parabola is parallel to the y-axis.
We compare the focus and the directrix to determine whether the parabola opens downwards or upwards.
If the directrix is above the focus, then the parabola opens downwards.
On the other hand if the directrix is below the focus , then the parabola must open upwards.
If you look at option C, y=-2 isthe directrix. The focus is (3,-5). Since the the y-value of the focus , -5 is less than y=-2 which is the directrix, this parabola must open down.
To find 10% divide by 10 so 1.07 or round to 1.08 if you like then double to get 20% so 2.14 or 2.16 so if the bill is 10.75 you would pay 12.89 with a 20% tip
