The answer is
A=1/2bh
So the base number times height number divided by two!!
46 divided by 3 would be the equation which you can round to 16
4 and a half to fill
30 in total minus the ones already used 30 - 18 = 12
A forth of the pages she wants to save which is about 7.5 of the total
12 - 7.5
Means she only has 4.5 pages left to use before she starts using her extra vacation pages
675 : 5 = 135
135 : 5 = 27
27 : 3 = 9
9 : 3 = 3
3 : 3 = 1
675 = 5 · 5 · 3 · 3 · 3 = 5² · 3³
