Answer:
Step-by-step explanation:
The formula for the arithmetic sequence is
[tex]a_{n}=a_{1}+d(n-1)[/tex], where
n is the position of the number you are looking for, a₁ is the first number in the sequenc, and d is the arithmetic difference (the difference between each number in the sequence). For us:
n = 20,
a₁ = 12, and
d = 3. ∴
our formula is this one:
[tex]a_{20}=12+3(20-1)[/tex] and
[tex]a_{20}=12+3(19)[/tex] and
[tex]a_{20}=12+57[/tex] so
a = 69
