math
posted by peter .
If # (a,b,c,d) means you take the positive value of the square root of each term, then add the resulting values, and # (a,36,16,9)=15, then a = ?
please explain

How about you giving this one a try ?
Just follow the steps they told you to take,
let me know what you get, and how you got it. 
square root(a+36+16+9)=15

I don't know how to translate word to math

No, you did not follow the instructions,
it says ...
take the square root of each number , THEN add them up, so
√a + √36 + √ 16 + √9 = 15
√a + 6 + 4 + 3 = 15
√a = 2
a = 4 
ok, I understand now , thank you