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6)9
7)48
8)a)2.5
b)125

2006-12-10 12:20:50 補充：
6)Let Teresa's age is X,Father's age is Y4X=Y.......1Y-X=27.......2Put 2 into 14X-X=273X=27X=27/3X=9So Teresa is nine yrs old.

2006-12-10 12:21:01 補充：
7)Let the larger no. is X, The smaller no.YX - Y = 8.....1X Y =88......X=88-Y......2Put 2 into 188 -2Y =8Y=40Put Y =40 into 2X 40 = 88So X = 48

2006-12-10 12:23:29 補充：
8)Let the price of book = X, Let the tissue's price is Y3X 6Y =$105.....1X=12Y....2Put 2 into 136Y 6Y =$10542Y = $105Y =$2.5SO Tissue price = $2.5The book price is 12 times of the tissue, So the price of the book =$2.5x12 =$30~~

6) Let Teresa's age is y and her father's age is z
z x 1/4 = y
z - y = 27

z - y = 27
z - (z x 1/4) = 27
z - z/4 = 27
3z/4 = 27
z = 36

z - y = 27
36 - y = 27
y = 9

Teresa's age is 9.

7) Let the larger number be y and the smaller number is z
y - z = 8
y + z = 88

z = y - 8

y + z = 88
y + (y - 8) = 88
2y - 8 = 88
y = 48

The larger number is 48.

8a) Let the price for book be y and the price for a pack of tissue be z
3y + 6z = 105
12z = y

6z = 105 - 3y
z = 17.5 - y/2

12z = y
12 x (17.5 - y/2) = y
210 - 6y = y
y = 30

12z = y
12z = 30
z = 2.5

The price for a pack of tissue is 2.5.

b) 4 books and 2 packs of tiss paper
4 x 30 + 2 x 2.5 = 125

6) let x be the age of Teresa's age
x=4x-27
x=9

7) let x be the larger number,
x+(x-4)=88
x=42

8a) let x be the price of a book
and y be the price of a pack of tissue paper

3x+6y=105-----------(1)
12y=x -----------------(2)
sub (2) in (1),,
3(12y)+6y=105
36y+6y=105
y=2.5-------------------(3)
sub (3) in (2)
12(2.5)=x
x=30

therefore a pack os tissue paper is $2.5

b) the price os 4 books and 2 packs of tissue paper
= 4x30+2x2.5
=$125