artaud noticed that if he takes the opposite of his age and adds 40 he gets the number 28. how old is artaud?

He is 12 years old

-12+40=28

Get it?

No can you work it out for me please

Well it says that the opposite of his age equals 40.

The opposite of a number is its negative. That is how we get negative 12.
When you add 40 to negative 12 you get 28 just like the problem says.

So

-12 negative twelve
plus
40 forty
equals
28 twenty eight

Thank you

28