Question 622176
Let n represent an odd integer.
now since consecutive means, 1,2,3 and in this case we are dealing with odd numbers, so 1,3,5 we have:

n+(n+2)+(n+4) = some number

now we know this number is between 21 and 39, so we rewrite this as an inequality.
 21< n+(n+2)+(n+4) <39 

now simplify and we get:

21<3n+6<39