An arithmetic sequence is shown below. You are not given many terms of this sequence, but you do have enough to fill in the missing number. What number goes in the blank?

12, _, 54, ...

Hello there.

An arithmetic sequence is shown below. You are not given many terms of this sequence, but you do have enough to fill in the missing number. What number goes in the blank?

12, _, 54, ...

33

For this, we use the equation for arithmetic sequence. It is given as:

an = a1 + (n-1) d

where an is the value at n term, a1 is the first term and d is the common difference

For 54,

54 = 12 + (3 - 1) d

d = 21

an = 12 + (2-1) 21

an = 33