a) (7x - 3) / (x - 1) = 2 / 3
<=> 3.(7x - 3) = 2.(x - 1)
<=> 21x - 9 = 2x - 2
<=> 19x = 7
<=> x = 7 / 19
b ) 2.(3 - 7x) / ( 1 + x) = 1 / 2
<=> 2 . 2 . (3 - 7x) = 1+ x
<=> 12 - 28x = 1 + x
<=> 29x = 11
<=> x = 11 / 29
c) (x + 1) / (x - 1) - (x - 1) / (x + 1) = 4/(x^2 - 1)
<=> ( (x + 1)(x + 1) - (x - 1)(x - 1) ) / ( (x -1).(x + 1) = 4 / (x^2 -1)
<=> ( x^2 + 2x +1 - x^2 + 2x - 1 ) / (x^2 - 1) = 4 / (x^2 -1)
<=> 4x = 4
<=> x = 1
d) (8 - x) / ( x - 7) - 8 = 1/(x - 7)
<=> (8 - x - 8(x - 7) ) / (x - 7) = 1/(x - 7)
<=> 8 - x - 8x + 56 = 1
<=> 9x = 63
<=> x = 7