This problem should be regarded as a problem of consumption and income.

First, three customers spent 100*3=300 yuan.

Then, Xiao Er changed 30 yuan.

Equal to customer consumption 300-30=270 yuan.

So, boss

Income 300 yuan. Because there is a special price.

So, the payoff is 300-50=250 yuan.

Finally, Xiao Er.

The boss gave others 50 yuan, but he only got back 30 yuan.

I packed 20 bucks myself.

So, Xiao Er earned 20 yuan. That is, the income is in 20 yuan.

The conclusion is:

Consumption equals 300-30=270.

Income equals:

Boss income+secondary income

250+20=270

Consumption equals income: 270=270.

Therefore, 10 yuan is not small.

The expression ability is not very good, so we just have a look.