20 . найдите значение выражения: 1)2 : (1 1/5 - 2,2) + 1/10 : (2,8 - 3/8) 2)(15/98 - 17/28) : 1 40/49 + (0,1 - 0,15)* 21 3/7

1.
2 : (1 1/5 - 2,2) + 1/10 : (2,8 - 3/8) = -1 93/97,

1) 1 1/5 - 2,2 = 1,2 - 2,2 = -1,
2) 2 : (-1) = -2,
3) 2,8 - 3/8 = 28/10 - 3/8 = 112/40 - 15/40 = 97/40 = 2 17/40,
4) 1/10 : 2 17/40 = 1/10 : 97/40 = 1/10 * 40/97 = 4/97,
5) -2 + 4/97 = -1 93/97,

2.
(15/98 - 17/28) : 1 40/49 + (0,1 - 0,15)* 21 3/7 = -1 9/28,

1) 15/98 - 17/28 = 30/196 - 119/196 = -89/196,
2) -89/196 : 1 40/49 = -89/196 : 89/49 = -89/196 * 49/89 = -49/196 = -1/4,
3) 0,1 - 0,15 = -0,05,
4) -0,05 * 21 3/7 = -1/20 * 150/7 = - 15/14 = -1 1/14,
5) -1/4 + (-1 1/14) = -1/4 - 1 1/14 = -7/28 - 30/28 = -37/28 = - 1 9/28