Irishman job interview

An Irishman applies for a job, but the foreman won't employ him until he passes a little maths test.
"Here's your first question, the foreman said.

"Without using numbers, represent the number 9."

"Without numbers?" the Irishman says, "Dat is easy." and proceeds to draw three trees.

"What's this?" the boss asks.

"Haven't you got a brain? Tree and tree and tree makes nine," says the Irishman.

"Fair enough," says the boss. "Here's your second question. Apply the same rules using the number 99, this time."

The Irishman stares into space for a while, then picks up the picture that he has just drawn and makes a smudge on each tree. "Dere you
go."

The boss scratches his head and asks, "How on earth do you get that to represent 99?"

"Each of da trees is dirty now. So, it's dirty tree, and dirty tree, and dirty tree. Dat equals 99."

The boss starts getting worried that he's actually going to have to give the Irishman the job, so he says,"

All right, final question: same rules again, but represent the number 100."

The Irishman stares into space for a while, then picks up the picture again and makes a little mark at the base of each tree and says,
"Dere you go. One hundred."

The boss looks at the illustration and bursts out: "You must be nuts if you think that represents a hundred!"

Whereby the Irishman leans forward and points to the marks at the base of each tree, saying:

"A little dog came along and crapped by each tree.So now you've got dirty tree and a turd, dirty tree and a turd, and dirty tree and a turd, dat makes one hundred. ...

So, when do I be starting the job?!"