Question

(x%2)≠0 what does this mean - i dont understand the symbols

Answer 1

% is used in a lot of programming languages as the modulo operator.

$a\%b=c\iff a\equiv c\mod b$

which is to say, the remainder upon dividing $a$ by $b$ is $c$.

When you divide any integer by 2, you can get either a remainder of 0 or 1. So in your example, $x\%2\neq0$ refers to all numbers $x$ between 1 and 9 that are not perfectly divisible by 2. In other words, $x\%2\neq0$ refers to those $x$ that are odd. (This assumes $B$ is a subset of the integers.)