Why can't 3/7 be written as a terminating decimal

Answer 1

because it is a repeating decimal
https://en.wikipedia.org/wiki/Repeating_decimal
namely 3 * (1/7) where 1/7 is a repeater

Answer 2

because it is a repeating decimal

there is a group of 6 digits that repeats continuously

3/7 = .

Answer 3

because it is a repeating decimal

there is a group of 6 digits that repeats continuously

3/7 = .428571428571...