Вычислите: 0,75:(-3/20)-8,4:(-2/3); 7,6:(-1цел4/15)-(-9,75):1цел1/12

а) 0,75 / (- 3/20) - 8,4 / (- 2/3) = 7 3/5.
    0,75 = 75/100 на 25 = 3/4.
    8,4 = 8 4/10 = 84/10 на 2 = 42/5.
    5 = 4 5/5 = (4 * 5 + 5)/5 = 25/5.
 1. 3/4 / (- 3/20) = - (3 * 20)/(4 * 3) = - 60/12 = - 5.
 2. 42/5 / (- 2/3) = - (42 * 3)/(5 * 2) = - 126/10 сократим на 2 = - 63/5.
 3. - 5 - (- 63/5) = - 25/5 + 63/5 = 38/5 = 7 3/5.
б) 7,6 / (- 1 4/15) - (- 9,75) / 1 1/12 = 3 3/4.
    7,6 = 7 6/10 = 76/10 на 2 = 38/5.
    1 4/15 = (15 + 4)/15 = 19/15.
    9,75 = 9 75/100 = 975/100 на 25 = 39/4.
    1 1/12 = (12 + 1)/12 = 13/12.
    6 = 5 4/4 = (5 * 4 + 4)/4 = 24/4.
 1. 38/5 / (- 19/15) = - (38 * 15)/(5 * 19) = - 570/95 = - 6.
 2. - 39/4 / 13/12 = - (39 * 12)/(4 * 12) = - 468/48 сократим на 12 = - 39/4.
 3. - 6 - (- 39/4) = - 24/4 + 39/4 = 15/4 = 3 3/4.