Question

Find the 17th term of the of the arithmetic sequence-5,0,5,10

Answer 1

An=a1+d(n-1)
first term is -5 (only way for it to make sense)
common difference is proabtly 5

an=-5+5(n-1)
17th term
an=-5+5(17-1)
an=-5+5(16)
an=-5+80
an=75
17th term is 75

Answer 2

The n-th term for an arithmetic sequence with a common difference of 5 and a first term of -5 is given by
  a(n) = -5 + 5(n-1)
or
  a(n) = 5n -10

The 17th term is found by evaluating this for n=17.
  a17 = 5·17 - 10
  a17 = 75