171. 1) (2/3 ) / (4/9*x - 4/9) +1/20 =4/5 ;(2/3)* 9 / (4/9*x - 4/9)*9 = 4/5 -1/20;2*3 / (4x -4) = 15 / 20 ;2*3/ 4(x -1) = 3/4 ; 3/ 2(x -1) = 3/4 ; 2(x - 1) =4 ;x-1 =2 ;x=3.=======171. 2) (5/7) / (6/7 *x + 3/7) - 1/2=1/6 ;(5/7) *7 / ( (6/7 *x + 3/7)*7 ) =1/6 +1/2 ;5/ (6x +3) =4 /6 ;5/ (3(2x +1) ) =2 / 3 ;3(2x +1) =5 : 2/3 ;3(2x+1) =15 /2 2x+1 = 15/2 : 3 ;2x+1 = 5/2 ;2x=5/2 -1 ;2x =3/2 ;x =3/4 .-----(5/7) / (6/7 *x + 3/7) - 1/2=1/6 ;5 / (6x+3) = 1/2+1/6 ;5/(3(2x+1) ) = 2/3 ; 5/(2x+1 ) = 2 ;2x+1 = 5 / 2 ; 2x =5/2 -12x =3/2 ;x =3/4