а) 19,6 × 2 1/5 + (5,25 × 1 1/5 -4,5 × 4/5 ) = 98/5 × 11/5 + ( 21/4 × 6/5 - 9/2 × 4/5 ) = 1078/25 + ( 21/2 × 3/5 - 9 × 2/5) = 1078/25 + (63/10 - 18/5) = 1078/25 + 25/10 = 2291/50 = 45 41/50 = 45,82
б) (3 1/3 - 1 5/6) ÷ 2 1/7 - 1 1/3 × 2,4 = ( 10/3 - 11/6 ) ÷ 15/7 - 4/3 × 12/5 = 3/2 × 7/15 -4 × 4/5 = 1/2 × 7/5 - 16/5 = 7/10 - 16/5 = - 5/2 = - 2 1/2 = -2,5