Lemme have a go at this.

20% of a number is 1/5 of the number

So we can do 1/5x50=10. So she has to pay $10 per delivery

(Btw that was the example that the problem gave I think)

Now we can use that mothod for all the prices

RIght now we are looking for emilies profit.

15->12

12->9.60

20->16

18->14.40

22->17.60

(Sorry that I didnt add the dollar sign I thought it would be confusing)

Now lets add them up

We will get $69.60 excluding the tip

Now we add the tip to it.

The total tip is $21

Now we add $21+69.60

**$90.60**