:

5 + √15 - √5:

√15 cannot be simplified any further, but √5 can be simplified to √5. Therefore, the expression simplifies to: 5 + √15 - √5.

3 + √6:

√6 cannot be simplified any further, so the expression stays the same: 3 + √6.

√15 - √3:

Both √15 and √3 cannot be simplified any further, so the expression stays the same: √15 - √3.