1.
2 18/31 * 12,4 - 2,75 : 4 5/7 =
= 80/31 * 124/10 - 175/100 : 33/7 =
= 80/31 * 124/10 - 175/100 * 7/33 =
= 8 * 4 - 49/132 = 32 - 49/132 = 31ц. 83/132,
2.
1 2/3 * 3,6 + 2 8/9 : 19,5 =
= 5/3 * 36/10 + 26/9 : 195/10 =
= 12/2 + 26/9 * 10/195 =
= 6 + 4/27 = 6ц. 4/27