2ц 7/15 - 2ц 2/15 - 8 ц 1/9 =
= 5/15 - 8ц 1/9 =
= 5/15 - (8*9+1)/9 =
= 5/15 - 73/9 =
= 1/3 - 73/9 =
= 1*3/3*3 - 73/9 =
= 3/9 - 73/9 =
= -70/9 =
= -7 ц 7/9
2ц 7/15 - 2ц 2/15 - 8 ц 1/9 =
= 5/15 - 8ц 1/9 =
= 5/15 - (8*9+1)/9 =
= 5/15 - 73/9 =
= 1/3 - 73/9 =
= 1*3/3*3 - 73/9 =
= 3/9 - 73/9 =
= -70/9 =
= -7 ц 7/9