12*(1 3/4x+5/8)=8 1/2

12 * (1 3/4x + 5/8) = 8 1/2,1 3/4x + 5/8 = 8 1/2 : 12,1 3/4x + 5/8 = 17/2 : 12/1,1 3/4x + 5/8 = 17/2 * 1/12,1 3/4x + 5/8 = 17/24,1 3/4х = 17/24 - 5/8,1 3/4х = 17/24 - 15/24,1 3/4х = 2/24 = 1/12,х = 1/12 : 1 3/4,х = 1/12 : 7/4,х = 1/12 * 4/7,х = 1/21