Can anyone tell me what this symbol means please?

It's a bit like "+", so "Z" and "Q" would be all integers and rational numbers

http://en.wikipedia.org/wiki/Set_(mathematics)#Basic_operations

Thanks!

The whole question is;
From the set of numbers,
¶ = { 64/4 , -8 , 0 , -1/9 , 6.4 , square root(4) , square root(-9) , square root(2.89) , cube root(144) }
state the two different classifications of the numbers denoted by (Z "U" Q)

Anyone knows what it means, can answer me please??

Z is a set of integers.
Q is a set of rational numbers.

64/4 = 16 is a part of Z and Q
-8 = -8/1 is a part of Z and Q
0 = 0/1 is a part of Z and Q
-1/9 is a part of Q
6.4 = 32/5 is a part of Q
sqrt(4) = 2 = 2/1 is a part of Z and Q
sqrt(-9) = sqrt(-1)*sqrt(9) = i*3 is neither a part of Z or Q (would be a part of C and H)
sqrt(2.89) = sqrt(289/100) = sqrt(289)/sqrt(100) = 17/10 is a part of Q
sqrt_3(144) = sqrt_3(2^4*3^2) = sqrt_3(2^3)*sqrt_3(2*3^2) = 2*sqrt_3(2*3^2) is neither a part of Z or Q

Z = {16, -8, 0, 2}
Q = {64/4, -8, 0, -1/9, 6.4, sqrt(4), sqrt(2.89)}

So......I still don't understand the question.
By the way, thanks for the explanation, Guest.
The answer is (Z "U" Q) = { 16 , -8 , 0 , -1/9 , 6.4 , 2 , sqrt(2.89) }??

Someone help please...

Your characteristics of each set are:
Z: A set of integers. So natural numbers with a sign (negative and positive) and zero. eg. -x, 0, x
Q: A set of rational numbers. A rational number is a division of two integers like 3/5

So Z ∪ Q = { 16 , -8 , 0 , -1/9 , 6.4 , 2 , sqrt(2.89) } if
Z = {16, -8, 0, 2} and
Q = {64/4, -8, 0, -1/9, 6.4, sqrt(4), sqrt(2.89)}

{ 64/4 , -8 , 0 , -1/9 , 6.4 , square root(4) , square root(-9) , square root(2.89) , cube root(144) } = Z ∪ Q ∪ R

With R being a set of real numbers R = {64/4 , -8 , 0 , -1/9 , 6.4 , square root(4) , square root(-9) , square root(2.89) , cube root(144)}

Yeah, thanks. I know that.
But the problem is I don't know what it means by two different classifications.