Answer: 
3c=273 
c=91
2c= 212
C= 106
c= 91+ 106= 197
so they will need 197 canoes total
Why:
So first you have to determine a set variable to represent the number of canoes, I chose C. Then you make an equation to represent the number of canoes 273 people will use if they group into 3's, from this I got 3c=273. Solve for C and get 91.
The remainder of the group which is 485-273= 212 will use canoes in groups of 2's. To represent this, 2c=212. Solve for C and get 106. Combine 106 and 91 to get the total number of canoes. 
        
                    
             
        
        
        
It’s not going to be C because 10 is already in the question
        
             
        
        
        
The mode of this is 8,10, and 5
        
             
        
        
        
498 is approximately 500
12 is approximately 10
500/10 = 50
So, 498/12 is approximately 50.