To solve this expression, we need to find a common denominator for the fractions involved. The common denominator for 15, 8.1, and 5 is 120.

Rewriting the fractions with the common denominator:
-1/15 = -8/120
3/8.1 = 37.037/120
1/5 = 24/120

Now, we can subtract the fractions:
-8/120 - 37.037/120 + 24/120

Combining the numerators:
(-8 - 37.037 + 24)/120

Simplifying the numerator:
(-21.037)/120

Dividing the numerator by the denominator:
-0.17530833333333333

Therefore, -1/15 - 3/8.1 + 1/5 is approximately equal to -0.17530833333333333.