Answer:
I only know number 7 sorry
Explanation:
Anyways.....
The solution she has in the bucket has 80% water (as you found out), including 14.4 fl oz. water in a total of 18 fl oz. solution.
Barbara will need to add ammonia, but only after removing some (x fl oz.) of the solution she has in the bucket.
If Barbara wants an 18 fl oz. bucket full of 25% ammonia, she will need to have in that bucket 18 × 0.25=4.5 fl oz. ammonia (25% ammonia) and
18 × 0.75=13.5 fl oz. water (75% water).
Barbara will have to start by removing some of that 80% water solution to end up with just 13.5 fl oz. water in the bucket. Removing x fl oz. of solution, gets rid of 0.8x fl oz. of water, leaving 14.4 - 0.8x fl oz. of water. since the amount of water needed is 13.5 fl oz. Our equation is
13.5 = 14.4 - 0.8x
13.5= 14.4 - 0.8x →→ 0.8x = 14.4 - 13.5 →→ 0.8x = 0.9 →→
→→ x=1.125 fl. oz
Therefore 1.125 (may need to round) fl. oz should be replaced with ammonia.
Hope this helps some of your stress.