The first two terms of an arithmetic sequence are a1 = 2 and a2 = 4. What is a10, the tenth term?

A (1) = 2

a (2) = 4

You can see that the terms are increasing by + 2.

so

a (1) = 2

a (2) = 4

a (3) = 6

a (4) = 8

a (5) = 10

a (6) = 12

a (7) = 14

a (8) = 16

a (9) = 18

a (10) = 20

your answer is a (10) = 20.