Пример с дробями 1/12+1/15-0,5

1/12 + 1/15 -0,5 = 5/60 + 4/60 - 5/10 = 9/60 - 5/10 = 9/60 - 30/60 = -21/60 = = -7/20

0.5=5/10=1/2 1/12+1/15-1/2=(1*5+1*4-1*30)/60=(5+4-30)/60= - 21/60= - 7/20