Could you show me a simple way to work these equations out?

I know this is probably very easy, but I just can't get my head round it, how would you go about working out the following equations?

2k/5 - k/2 = 1

a/3 + a/5 = 1

x/2 + x/3 + x/4 = 1

Many thanks

$k\left(\frac{2}{5} - \frac{1}{2}\right) = 1 \iff -\frac{k}{10} = 1$.

i,e: 2/5 lots of k minus half a lot of k gives -1/10 lots of k.

So now you want to find a number such that if you multiply it by -1 and divide it by 10 you get 1.

This number is trivially $k = -\frac{10}{1}$.

Can you go through a similar procedure for the other questions now?

What is a/3 + a/5? i.e: 1/3 lots of a added to 1/5 lots of a?

Okay so I did that and got an answer of 9, but e book says the answer is 6, what did I do wrong?

Can't tell what question you're talking about.

Can't read minds and don't know what you've done. So you'll need to show me what you've done before I can point out where you've gone wrong.