Answer:
81
Explanation:
the formula for an arithmetic sequence:
aₙ = a₁ + (n-1)d
where aₙ = the nth term
a₁ = the 1st term = -3
n = the term number = 13
d = the common difference = 7
Plugging in those values into the formula to find a₁₃:
a₁₃ = -3 + (13-1)7
= -3 + (12)7
= -3 + 84
= 81