96 times 19 / 93 and 3 / 5 times 7 plus 0.6 times 4-3 / 5

96 times 19 / 93 and 3 / 5 times 7 plus 0.6 times 4-3 / 5

96 × (19 / 93) = (93 + 3) × (19 / 93) = 19 + 19 / 31 = 19 and 19 / 31 (3 / 5) × 7 + 0.6 × 4 - (3 / 5) = 0.6 × (7 + 4-1) = 0.6 × 10 = 6

How to calculate 1994 times 1994 minus 1993 times 1995
1994 times 1994 minus 1993 times 1995 is the denominator

A: please indicate which is the numerator and which is the denominator,
1994 times 1994 minus 1993 times 1994 of 1995
(in the supplementary note: 1994 times 1994 minus 1993 times 1995 is the denominator)
=1994/(1994×1994-1993×1995)
=1994/[1994×1994-(1994-1)×(1994+1)]
=1994/[1994²-(1994²-1)]
=1994/1
=1994

3.6×25.4+37.9×6.4
This is a Mathematical Olympiad problem
Divide the rate by multiplication

3.6×25.4+37.9×6.4
=3.6×25.4+(25.4+12.5)×6.4
=3.6×25.4+25.4×6.4+12.5×6.4
=3.6×25.4+25.4×6.4+12.5×8×0.8
=25.4×(3.6+6.4)+100×0.8
=254+80
=334

What is the product of 2 / 3 minus 1 / 4 multiplied by the reciprocal of 20 / 21?

（2/3-1/4）*21/20=（5*21）/（12*20）
Upper and lower approximations = 7 / 16