Answer:
hi, quick tip
go to cymath or just screenshot the equations or put it in, and it will automatically solve it for you instead of having to wait for someone to answer. 
hope this works :}
Step-by-step explanation:
 
        
                    
             
        
        
        
8x+11=315 where x = the number of students on each bus
x = 38 students
        
             
        
        
        
Answer:
34 feet
Step-by-step explanation:
From the question, we are told that:
 If the room is 30 feet high at the center and 90 feet wide at the floor, 
Entire width of the room = 90 feet = 2a
a = 90/2 = 45
Height of the room = b = 30 feet
Foci (c)² = a² - b²
c = √a² - b²
c = √45² - 30²
c = √1125
c = 33.541019662 feet
Approximately to the nearest whole number = 34 feet 
Denise and Donna should each stand 34 ft from the outer wall so that they will be positioned at the foci of the ellipse