Amanda pours 3/4 of her water into Barbara’s empty bottle. Barbara then pours 3/5 of her water into Charlie’s empty bottle. Charlie then pours 1/2 of his water into David’s empty bottle. If David now has 18 ounces of water, how many ounces does Amanda still have?

20 ounces of water

Step-by-step explanation:

Work backwards. David has 18 ounces, which is half of Charlie's. So, Charlie had 18•2=36 ounces. That was 3/5 of Barbara's water, so Barbara had 60 ounces. That is 3/4 of Amanda's water, so Amanda had 80 ounces. To find how much Amanda had left subtract 60 from 80 to get 20.

step-by-step explanation:

we have

using a graphing tool

see the attached figure

this is a quadratic equation (vertical parabola) open up

the vertex is a > vertex

the domain of the function is all real > interval (-∞,∞)

the range of the function is the > [-6.125,∞)

the function has two x->   and

the function is increasing over the > (0.25,∞)

the function is decreasing over the > (-∞,0.25)