Jeff is choosing a shrub and a rose tree for his garden. At the garden centre there are 17 different types of shrubs and some rose trees.

Jeff says,

"There are 215 different ways to choose one shrub and one rose tree."

Could Jeff be correct?
You must show how you get your answer.

This question has 2 part(s).

There are 12 boys and 10 girls in David's class.
David is going to pick three different students from his class and write their names in a list in order.

The order will be

How many different lists can David write?

$a$ is a prime number.

$b$ is an even number.

$N={a}^{2}+ab$

Circle the correct statement about $N$.