А)
Числитель:
20 : 2 2/15 + 25 5/7 : 1 1/35 =
= 20/1 * 15/32 + 180/7 * 35/36 =
= (5*15)/(1*8) + (5*5)/(1*1) =
= 75/8 + 25 = 9 3/8 + 25 = 34 3/8
Знаменатель:
21 7/9 : 4 2/3 - 1 =
= 196/9 * 3/14 - 1 =
= (14 *1) / (3*1) - 1 =
= 4 2/3 - 1 = 3 2/3
Получается дробь:
(34 3/8 ) / ( 3 2/3 ) = 275/8 : 11/3 =
= (275 * 3)/(8 * 11) = (25*3)/(8*1) = 75/8 =
= 9 3/8 =
= 9,375
б)
Числитель:
6 3/4 : 9 + 24 : 6/7 - 1/9 : 4/21 =
= 27/4 * 1/9 + 24/1 * 7/6 - 1/9 * 21/4 =
= 1/9 * (27/4 - 21/4) + (4*7)/(1*1) =
= 1/9 * 3/2 + 28 =
= (1 * 1) /(3*2) + 28 =
= 1/6 + 28 = 28 1/6
Знаменатель :
53 2/3 - 22 14/15 : 2 2/3 =
= 53 2/3 - 344/15 * 3/8 =
= 53 2/3 - (43*1)/(5*1) =
= 53 2/3 - 8 3/5 =
= 53 10/15 - 8 9/15 =
= 45 1/15
Получается дробь:
(28 1/6) / (45 1/15) =
= 169/6 * 15/676=
= (1*5)/(2*4) =
= 5/8 =
= 0,625