Regarding your (1/10 divided by 2/5): I'm going to regard this as
(1/10) divided by (2/5).
First, write
1
---
10
Invert the fraction 2/5 and then multiply 1/10 by 5/2:
1(5)
-------- = 1/4, after reducing 5/10.
10(2)
Thus, −34+(1/10÷2/5) yields -34 + 1/4, or -33 3/4.