There's so little to this problem, and it will do you so much more good to work it out yourself, that I'm just going to point you in the right direction and give you a little push:
The area of a triangle is half of the product of its base and height.
A = (1/2) (base) (height)
I know you know what the base and height are, because you just told them to US.
Base = 7.5m = 750 cm Height = 6 cm.
Write those numbers in the formula in place of the words:
<span> A = (1/2) (base) (height)</span>
A = (1/2) (750 cm) (6 cm) .
Do that multiplication, and you've got your area.
Don't forget to keep the units when you multiply, so that the answer is in units of cm² .
The answer may be a big number, and you may want to change it to meter² instead of cm², to make it a smaller number.
Jane has 2 times as many books as Jill, so there are 3 parts. Two parts Jane and one part Jill. So, divide 216 by 3 and it's 72, which equals one part. Jane has two parts, so 72 x 2. Jane has 144 books.
