To simplify this expression, we first need to find a common denominator for the fractions.

$5/6-3/10$ = $25/30-9/30$ = 16/30 = 8/15

$3/10+2/15$ = $9/30+4/30$ = 13/30

So, $5/6-3/10$ / $3/10+2/15$ = $8/15$ / $13/30$

To divide by a fraction, we can multiply by the reciprocal:

$8/15$ / $13/30$ = $8/15$ * $30/13$ = 240/195 = 48/39 = 16/13

Therefore, $5/6-3/10$ / $3/10+2/15$ simplifies to 16/13.