Answer:
The maximum speed of Hal's airplane in still air is:

The speed of the wind

Step-by-step explanation:
Remember that the velocity v equals the distance d between time t.
and 
The distance that Hal travels when traveling with the wind is:
miles
Where v is the speed of Hal and c is the wind speed.
The distance when traveling against the wind is:
miles
Now we solve the first equation for v




Now we substitute the value of v in the second equation and solve for c







Then:


The maximum speed of Hal's airplane in still air is:

The speed of the wind

Percentage of people who buy Burgers = 35+45/2 = 80/2 = 40
Total Number of people = 900
So, 900 * 40%
= 900 * 0.40
= 360
In short, Your Answer would be: 360 burgers
Hope this helps!
3y + 5x = -15
3y = -5x - 15 (Subtract 5x from both sides)
y = -5/3x - 5 (Divide everything by 3)
Try C but im not 100% sure though