Function composition I'm looking over practice exam papers and i've came across function composition. I can't do it. I've been given some notes with predone ones but cannot get the hang off it 

here are the predone ones
in a way they do make sense, from a third person perspective but as soon as they're gone and i've gotta answer it myself i'm clueless. I'd be really grateful if someone could lay some questions out with the basic steps for doing them. Thanks

Just carefully evaluate from the inside out by substitution, checking that the value lies in the appropriate domain. 
The $(g \circ h(3))=g(h(3))$ example makes no sense, as $h(3)$ is either $\text{true}$ or $\text{false}$, and $g$ is defined on the reals.
Another example, if $y=(h \circ f \circ g) (5) = h(f(g(5)))$.
Then $g(5) = 2 \cdot 5 +2 = 12$, so $y=h(f(12))$.
Now $f(12) = {12 \over 3}= 4$, so $y=h(4)$.
Finally, $h(4) = (4 < 10) = \text{true}$, so we have $y=\text{true}$.
