求人幫我解方程

(1)
5y/3 - 6 = 2y - 9
Multiply all terms by 3, we get
5y - 18 = 6y - 27
27 - 18 = 6y - 5y
y = 9.
(2)
(2x + 7)/3 = (4x + 1)/5 - 2
LCM of 3 and 5 is 15, so multiply all terms by 15, we get
5(2x + 7) = 3(4x + 1) - 30
10x + 35 = 12x + 3 - 30
35 - 3 + 30 = 12x - 10x
62 = 2x
x = 31
(3)
(x + 9)/7 - (3x - 2)/4 = x + 5
LCM of 7 and 4 is 28, so multiply all terms by 27, we get
4(x + 9) - 7(3x - 2) = 28(x + 5)
4x + 36 - 21x + 14 = 28x + 140
28x + 21x - 4x = 36 + 14 - 140
3x = - 90
x = - 30.

2014-01-01 07:56:17 補充：
Remark : Q3 should read ' multiply all terms by 28', not 27. Sorry for the typing error.

5y/3-6=2y-9

3*(5y/3-6)=3*(2y-9)

5y-18=6y-27

-18=y-27

27-18=y

9=y

y=9



2x+7/3=4x+1/5-2

15*(2x+7/3)=15*(4x+1/5-2)

30x+35=60x+3-30

35=30x-27

62=30x

62/30=x

x=31/15



x+9/7-3x-2/4=x+5

28*(x+9/7-3x-2/4)=28*(x+5)

28x+36-84x-14=28x+140

-56x+22=28x+140

22=84x+140

-118=84x

-118/84=x

x=-59/42

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