1.а) 5/6 - 5/12=2*5/2*6-1*5/1*12=10/12-5/12=10-5/12=5/12
б) 2/5*3 1/3=2/5*3*3+1/3= 2/5*10/3=2*10/5*3=20/15=4*5/3*5=3/4=1 1/3
в) 4-3 2/8=4/1-3 2/8=4/1-3*8+2/8=4/1-26/8=8*4/8*1=1*26/1*28=32/8-26/8=32-26/8=6/8=3*2/4*2=3/4
17%=17/100
680:17/100=680*100/17=4000/1=4000
(2x-3)(х+7) = (x-4)(2x+3) + 3,
2х² + 14х - 3х - 21 = 2х² + 3х - 8х - 12 + 3,
14х - 3х - 3х + 8х = -12 + 3 + 21,
16х = 12,
х = 12/16,
х = 3/4 ( или х = 0,75 )