The answer to your problem is 58/90
Using proportions, it is found that the speed of the runners are of 16 mph and of 20 mph.
<h3>What is a proportion?</h3>
A proportion is a fraction of a total amount.
After 30 minutes, the runners are 2 miles apart, hence the second runner is 4 miles per hour faster than the second, that is:
.
The first runner's speed is 4/5 of the speed of the second runner, hence:





Hence, the speed of the runners are of 16 mph and of 20 mph.
More can be learned about proportions at brainly.com/question/24863377
One interpretation of your intent would be as follows:
16x^11y^8
Find 4 √ [-----------------]. Is that what you meant?
81x^7y^6
4*x^5*√x*y^4
If so, then the correct result would be 4 ---------------------
9*x^3*√x*y^3
and this could be reduced to:
4*x^5 * y^4 * √(x) 4*x^2*y
4 --------------------------- = -------------
9*x^3*y^3 √(x) 9
C. 56
Hope this helped lol I needed more characters