To find a11 in an arithmetic sequence, we need to use the formula for the nth term of an arithmetic sequence:
a_n = a_1 + (n-1)d
where a_n is the nth term, a_1 is the first term, n is the number of the term we want to find, and d is the common difference between consecutive terms.
We know that a_1 = 16 and a_7 = -26. We can use this information to find the common difference:
a_7 = a_1 + 6d
-26 = 16 + 6d
-42 = 6d
d = -7
Now that we know the common difference, we can use the formula to find a_11:
a_11 = a_1 + (11-1)d
a_11 = 16 + 10(-7)
a_11 = -54
Therefore, a11 in the arithmetic sequence is -54.