一元一次方程題題!!請幫忙!

1)
設較大的數為x
x*3 - (x-18) = 78
3x - x + 18 = 78
2x = 60
x = 30
較小的數則為 x - 18 = 12
兩數之和 = 42

2)
3x + 3 = 5x - 11
2x = 14
x = 7
面積 = (3x+3)^2
= 24^2 =576

3)
面積 = 1/2 底*高
9/2 (10-2x) = 7-x
45 - 9x = 7-x
8x = 38
x = 38/8

4)
設求較大的數為 x
x+(x-22) = 56
2x = 78
x = 39

5)
設女生 x 人
x + (x + 8) = 44
2x = 36
x = 18
女生有 18人

1)
設y>x
y-x=18...(1)
3y-x=78...(2)
(2)-(1):
2y=60
y=30
代y=30入(1):
30-x=18
x=12
這兩個數的和=12+30=42

2)
3x+3=5x-11
x=7
正方形的面積=x^2=7^2=47

3)
(10-2x)*9/2=7-x
45-9x=7-x
8x=38
x=4.75

4)
設y>x
x+y=56...(1)
y-x=22...(2)
(1)+(2):
2y=78
y=39
較大的數=39

5)
m-f=8...(1)
m+f=44...(2)
(2)-(1):
2f=36
f=18
女生人數=18

2007-07-31 00:18:29 補充：
2)3x 3=5x-11x=7正方形的面積=(3x 3)^2=(3*7 3)^2=576

(1) 設某數= x, 設大數 = y
y = x + 18,
78 = 3y - x = 3(x + 18) - x
78 = 2x + 54
x = 12, y = 30, x + y = 42

(2) 因正方形是等邊, 3x + 3 = 5x -11
x = 7, 邊長 = 24, 面積 = 24^ 2 = 576

(3) 面積 = (10 - 2x) 9 / 2 = (7 - x)^2
90 - 18x = 98 - 28x + 2x^2
2x^2 - 10x + 8 = 0
x^2 - 5x + 4 = 0
(x - 4) (x - 1) = 0
x = 4 , or x = 1
(4) x + y = 56 ------(1) , x - y = 22 -------(2)
(1) + (2) : 2x =78, x =39, y = 17 大數 = x = 39

(5) 男生 = x人, 女生 = y 人
x+y = 44 ------(1) , x - y = 8 ------(2)
(1) - (2) : 2y = 52, y = 26 女生有26人