a1=17 d=3 a18=?

To find the value of \( a_{18} \) in an arithmetic sequence where \( a_1 = 17 \) and the common difference \( d = 3 \), you can use the formula for the \( n \)-th term of an arithmetic sequence:

\[ a_n = a_1 + (n - 1) \cdot d \]

For \( n = 18 \):

\[ a_{18} = a_1 + (18 - 1) \cdot d \] \[ a_{18} = 17 + (17) \cdot 3 \] \[ a_{18} = 17 + 51 \] \[ a_{18} = 68 \]

Thus, \( a_{18} = 68 \).