Answer:
15 ml
Step-by-step explanation:
If we mix 1 part concentrate and 5 parts water, we have 6 parts in total.
To create 90ml medicine, <em>how many "6 parts" are there?</em>
There would be 90/6 = 15 total "6 parts".
Each of the "6 parts's" 1 part is concentrate, so concentrate would be 1 * 15 = 15 ml.
<u>In ratio:</u>