(5/18 + 7/12 ) * 2 10/31 + 1 13/51 : (4/17 - 20/51 ) =
выражением:
= ( 10/36 + 21/36 ) * 72/31 + 64/51 : ( 12/51 - 20/51 ) =
= 31/36 * 72/31 + 64/51 : (- 8/51 ) =
= 2 - 64/51 * 51/8 = 2 - 8 = -6
по действиям:
1) 5/18 + 7/12 = 10/36 + 21/36 = 31/36
2) 4/17 - 20/51 = (4*3 - 20)/51 = - 8/51
3) 31/36 * 2 10/31 = 31/36 * 72/31 = (1*2)/(1*1) = 2
4) 1 13/51 : (- 8/51) = 64/51 * (- 51/8) = - 64/8 = -8
5) 2 + (-8) = - (8-2) = - 6