Answer:
2 
Step-by-step explanation:
The question state that;  the sum of a number, 1/6 of that number, 2 1/2 of that number, and 7 is 12 1/2. Find the number.
First, we need to interpret and represent this statement mathematically
Let n be the number.
The sum means 'addition'
1/6 of that number is  1/6 of n = 1/6 × n  = 
2 1/2 of that number is 2 1/2 of n = 2 1/2 × n  = 5/2 × n = 
So the question says that, when we add;  ,
 ,   and 7 all together, the value is 12 1/2
  and 7 all together, the value is 12 1/2
That is;
  +
  +  + 7 = 12 1/2
 + 7 = 12 1/2
  +
  +  + 7  =
 + 7  =  ( changing 12 1/2 to improper fraction will give
         ( changing 12 1/2 to improper fraction will give   )
 )
So we can now go ahead and solve for n 
 +
  +  + 7  =
 + 7  =  
  
subtract 7 from both-side of the equation
 +
  +  =
   =   -   7
   -   7
 =
  =   
 =
      =    
 can be reduced to give us
  can be reduced to give us 
  =
   =   
Cross multiply
8n × 2  = 11× 3
16n = 33
Divide both-side of the equation by 16
 =
    =   
(On the left-hand side of the equation, 16 will cancel-out 16 leaving us with just, while  on the right-hand side of the equation 33 will be divided by 16)
n =   =
     = 
Therefore the number is  