Add a detailed explanation:

This is a trap of thinking, and it can't be counted like this. The boss should have charged 30-5=25 yuan, but now he swallowed two yuan, and * * * charged 25+2=3*9=27 yuan.

(0. 1÷0.2+0.3)÷0.4×0.5= 1

( 1+2)÷3+(4+5)= 10

The thick ones are in brackets.

Hope to adopt ~