Answer
5 nodes. 7 nodes.
Work Step by Step
Please see the attached diagram.
Not counting the endpoints, there are 5 nodes in a standing wave that contains three full wavelengths.
Not counting the endpoints, there are 7 nodes in a standing wave that contains four full wavelengths.
In general, not counting the endpoints, there are (2n - 1) nodes in a standing wave that contains n full wavelengths.