Answer:
- 1 bus, 72 vans
- $6960 is the minimum cost
Step-by-step explanation:
A bus costs over $19 per student; a van costs less than $12 per student. The required number of students could be transported by 81 vans, but that requires 81 chaperones. 
Since there are only 80, and a bus requires fewer chaperones per student, we can reduce the number of required chaperones to an acceptable level by employing one bus. 1 bus replaces 9 vans, and requires 1 less chaperone than 9 vans.
The minimum cost is 1 bus and 72 vans. That cost is $1200 +72×$80 = $6960.
 
        
             
        
        
        
<span>2x+ y = 3
x = 2y - 1 
Make sure there are NO SPACES in your answer. Include a comma in your answer.
It looks like I could substitute the x=2y-1. Into 2x+y=3
2(2y-1)+y=3
4y-2+y=3
5y=5
y=1
x=2(1)-1
x=1
(1,1)
CHECK
2x+y=3
2(1)+(1)=3
2+1=3
3=3
Left hand side=Right hand side 
Check other equation 
x=2y-1
1=2(1)-1
1=1
Therefore the solution is (1,1). Since the left hand side= right hand side in each equation</span>
        
             
        
        
        
Answer:
7 P.M. 
Step-by-step explanation:
Time at which the walk was begun = 4 p.m. 
Finished after rotating the clock 90° i.e. = 3 hours
Thus,
The time at which the task finished = 4 p.m. + 3hours
= 7:00 PM