Evaluate

15/root 10 +root20 +root40 -root 5 - root80

using root5=2.236, root 10=3.162

Here is the link for the answer similar to your query:
https://www.meritnation.com/ask-answer/question/find-the-value-of-6-root5-root3-it-being-given-that-root-3/number-systems/2685348 
Follow the second solution of the above link. From here you can evaluate the denominator part of the expression.