elemantary school so
area=legnth times width
to get greatest area, make legnth as close to width as possible in measure
to get least area, make legnth as far away from width as possible in measure
perimiter=2 times legnth+2 times width=2 times (legnth+width)
18=2 times (legnth+width)
divide 2
9=legnth+width
find closest and farthest
1+9 is farthest
4+5 is closest
areas=legnth times with
1 times 9=9
4 times 5=20
differnce is subtract
20-9=11
answe is 11
(note I didn't use decimals since the user is supposedly in elemenatry school)