Little Johnny...

Little Johnny arrived home from school with a note from the teacher for his mother.

She read the note and sighed.

"Really Johnny. Swearing in class. Your father will have to deal with this."

Later on Little Johnny is with his father.

"What this I hear about you swearing in school?" he growled.

"Well I'll tell you what happened," Little Johnny said. "I was asked what nine plus seven was and I said sixteen."

"That's right," said his father.

"Then I was asked what seven and nine equals."

"What's the difference?" asked his father.

"That's just what I said," replied Little Johnny.