Rough estimate: We expect the three forces to each be less than 10 N, based on some quick trial and error. If the first force is 2 N, the second will be about 8 N (that's 6 N more) and 2 + 8 = 10. Our third force is 5 times the first, somewhere near the 4 times that what we need.

Let the first force be F.

The second sentence tells us that:

• the second force is F + 6.4, and
• the third force is 4F.

The first sentence tells us that the sum of the first 2 forces equals the third force. So

So F = 3.2

The second force is F + 6.4 = 3.2 + 6.4 = 9.6

The third force is 4F = 4 × 3.2 = 12.8

So the 3 forces are: 3.2 N, 9.6 N and 12.8 N.