Math,help!!! Eng!!+20!!

1
Let a meters be the length of the garden
a-2.5 meters the width of the garden

2[a+(a-2.5)] = 45
2a-2.5=22.5
2a=22.5+2.5
a=12.5

therefore the length of the garden is 12.5 meters and the width of garden is (12.5-2.5)=10meters

2
Let m feet be the length
n feet be the width

as (m)(n) = 192
m = 192/n

2(m+n)=56
2[(192/n)+(n)] =56
(192+n^2)/n =28
n^2+192=28n
n^2-28n+192=0
(n-16)(n-12)=0
n-16=0 or n-12=0
n=16 or n=12

m = 192/n

m= 192/16 or m= 192/12
m=12 or m=12

therefore the dimension should be (12feet x 16feet) or (16feet x 12feet)


3
let y feet be the width
3y feet be the length

y+y+3y+3y=48
8y=48
y=6

therefore the length is (3)(6) = 18 feet and the width is 6 feet

4
Let f years old be the age of Francie
since Francie Angie are twins, Angie's age is also f years old
the age of Denise is f/2 years old

f+f+f/2 =45
5f/2=45
5f=90
f=18

therefore the age of Francie and Angie is 18 years old
the age of Denise is 18/2 = 9 years old

2008-05-30 18:57:40 補充：
since Francie and Angie are twins, the age of Angie is also f years old

2008-05-30 18:58:33 補充：
m= 192/16 or m= 192/12
m=12 or m=12 (打錯了)

m=12 or m=16