Can someone give me an explanation to ellipse formula please

To derive the equation of an ellipse centered at the origin, we begin with the foci (−c,0) and (c,0). Theellipse is the set of all points (x,y) such that the sum of the distances from (x,y) to the foci is constant, as shown in Figure 5.

she played for 18.75 hours.

step-by-step explanation:

if she played 2/4 of a hour on tuesday. and there is 60 minutes in an hour and 60 divided by 4 is 7.5. and she played 2/4 of an hour on thursday then again 60 divided by 4 is 7.5, you add 7.5+7.5=56.25. now you have to do 1/4 of an hour, it equals 3.75. now you have to add them all up. 3.75+7.5+7.5=18.75

i hope this and i hope you get it right. it took me a while to get this done for you. : )