Not including the endpoints, there are 3 nodes.
What is a node?
In a wave, a node is a stationary point. For example in a vibrating string of a guitar, the endpoints would be nodes.
But here we need to ignore the endpoints, we only know that the wave has two wavelengths.
For a wave with N wavelengths the number of nodes that are not endpoints is just given by 2*N - 1 (while if we counted the endpoints we would have 2*N + 1).
So in this case we have N = 2, then there are 2*2 - 1 = 3 nodes.
If you want to learn more about waves, you can read:
https://brainly.com/question/14015797
