12*(одна целая 3/4х+5/8)=восемь целых 1/2
12 *(1 3/4 х + 5/8) = 8 1/2 12 *(7/4 х +5/8) = 8 1/2 21х + 60/8 = 17/2 21х = 17/2 - 60/8 21х = 68/8 - 60/8 21х = 1 х = 1/21
12*(7/4х + 5/8)= 17/2, 21х+ 15/2-17/2 = 0, 21х = 17/2-15/2, 21х = 1, х = 1/21.