Answer:
36cm
Explanation:
The lightning bolt on the right is 3 times bigger than the one on the left. You can tell this because that leftside, vertical-ish piece (on both of them) is labelled. The small one is 25cm and the big one is 75cm.
25 × 3 = 75
The bottom right side is 12cm, so times by 3 to find the bigger one that matches.
12 × 3 = 36