To find the common difference in the arithmetic sequence, you subtract the first term from the second term (or any two consecutive terms).
Here, the first term \( a_1 = 34 \) and the second term \( a_2 = 64 \).
The common difference \( d \) can be calculated as follows:
\[ d = a_2 - a_1 = 64 - 34 = 30 \]
Thus, the common difference in the arithmetic sequence is 30.