The statement holds because 2 and 4 divide 8. However, checking 2 and 4 is not enough for 8; for instance, 12 is divisible by both 2 and 4, but not 8.
Class 9 Maths Ganita Manjari Part 2 chapter 9 Propositions and their Converses solutions
Class 9 Maths Ganita Manjari Part 2 of Chapter 9 solutions