In an arithmetic series, the value of the nth term is calculated using the equation, an = ao + (n - 1)(d) where an and ao are the nth and the 1st term, respectively. d is the common difference, and n is the number of terms.
In the given, an = 48, a0 = 93, d = -5 and n is unknown. Substituting the known values, 48 = 93 + (n - 1)(-5) The value of n from the equation is 10. Thus, the answer is the last choice.