найдете значение выражения: а)21/20 -3/8-1/5. б)13/15-(1/5+1/6)

а) 21/20 - 3/8 - 1/5 = 42/40 - 15/40 - 8/40 = 19/40б) 13/15 - (1/5 + 1/6) = 26/30 - (6/30 + 5/30) = 26/30 - 11/30 = 15/30 = 1/2