31/7-7,425+(-6,425)*3 1/7 и (-4,5)-5 целых1/5+(-5,5)-5целых 1/3

3 1/7 - 7,425 + (-6,425) * 3 1/7 = - 24,475
1) - 6,425 *  3 1/7 = - 6425/1000 * 22/7 = - 257/40 * 22/7 = - (257*11)/(20*7) = - 2827/140 = - 20 целых 27/140
2) 3 1/7 - 7,425 = 3 1/7 - 7 425/1000 = 3 1/7 - 7 17/40 = 3 40/280 - 7 119/280 = - 4 целых 79/280
3) - 20 27/140 + (-4 79/280) = - 20 54/280 - 4 79/280 = - 24 133/280 = - 24 целых 19/40 = - 24,475 
и
(-4,5) - 5 1/5 + (-5,5) - 5 1/3 = - 20 целых 8/15
1) - 4,5 - 5 1/5 = - 4,5 - 5,2 = - 9,7
2) - 9,7 + (-5,5) = - 9,7 - 5,5 = - 15,2 = - 15 целых 1/5
3) - 15 1/5 - 5 1/3 = - 15 3/15 - 5 5/15 = - 20 целых 8/15