There's a rule where the the sum of the lengths of any two sides of a triangle has to be greater than the length of the third side So, add the two smallest numbers of each triangle and see if it is greater than the biggest number:
A: 10+13=23 and the longest side is 22. 23 is more than 22, so 'B' can be a triangle! We know this is an answer, but we should always check to see if any other answers work.
C: 12 + 7 = 19, and the longest side is 19. 19 isn't more than 19, so the answer isn't C.
B: 7 + 11 = 18, and the longest side is 24. 18 isn't more than 24, so the answer isn't B.
D: 6 + 9 = 15, and the longest side is 21. 15 isn't more than 21, so the answer isn't D.
Answer 'A' is the only one that can make a triangle, so it's the right answer!
Hope I helped, let me know if you have any questions :)