This an Arithmetic Progression question: (odd number: 1,3,5,7,...)
1st term a₁ = 1
the common difference is d=2
a term of rank n in a AP = a₁ + (n-1)d, where n = rank of the term.
Now let's apply the formula
a₈₇ = a₁ + (87-1).2
a₈₇ = 173
Hmm could you take a pic of this problem and add it so I can see what it looks like?
It would be 12x-3y because 10 + 2 is 12