Explanation:
Consider the first sequence:
15, 20, 25, 30, 35,...
Note that each term is increased by 5 from its previous term.
Therefore,

If the pattern continue, the next three term of the sequence will be:




Similarly,




Similarly,




Thus, the next three term of the sequence 15, 20, 25, 30, 35,... is 40, 45, and 50.
Now, consider the second sequence:
5, 9, 13, 17, 21,...
Note that each term is increased by 4 from its previous term.
Therefore,

If the pattern continue, the next three term of the sequence will be:




Similarly,




Similarly,




Thus, the next three term of the sequence 5, 9, 13, 17, 21,... is 25, 29, and 33.