Hard Arithmetic Puzzles

#3924: 8 _ 6 _ 3 _ 4 = 20 hard #3935: 8 _ 6 _ 3 _ 5 = 20 hard #3940: 8 _ 6 _ 3 _ 9 = 13 hard #3945: 8 _ 6 _ 4 _ 6 = 17 hard #3950: 8 _ 6 _ 4 _ 1 = 13 hard #3951: 8 _ 6 _ 4 _ 2 = 14 hard #3953: 8 _ 6 _ 4 _ 4 = 16 hard #3955: 8 _ 6 _ 4 _ 5 = 17 hard #3957: 8 _ 6 _ 4 _ 6 = 18 hard #3959: 8 _ 6 _ 4 _ 7 = 19 hard #3961: 8 _ 6 _ 5 _ 3 = 18 hard #3964: 8 _ 6 _ 5 _ 3 = 20 hard #3965: 8 _ 6 _ 6 _ 4 = 17 hard #3966: 8 _ 6 _ 6 _ 9 = 12 hard #3970: 8 _ 6 _ 8 _ 4 = 20 hard #3976: 8 _ 6 _ 8 _ 3 = 18 hard #3979: 8 _ 6 _ 9 _ 6 = 12 hard #3982: 8 _ 6 _ 9 _ 3 = 16 hard #3983: 8 _ 6 _ 9 _ 1 = 13 hard #3984: 8 _ 6 _ 9 _ 2 = 14 hard #3987: 8 _ 6 _ 9 _ 3 = 15 hard #3990: 8 _ 6 _ 9 _ 4 = 16 hard #3993: 8 _ 6 _ 9 _ 5 = 17 hard #3995: 8 _ 6 _ 9 _ 6 = 18 hard #3998: 8 _ 6 _ 9 _ 7 = 19 hard #4000: 8 _ 6 _ 9 _ 8 = 20 hard #4003: 8 _ 7 _ 2 _ 8 = 20 hard #4007: 8 _ 7 _ 4 _ 1 = 15 hard #4008: 8 _ 7 _ 4 _ 1 = 13 hard #4009: 8 _ 7 _ 4 _ 2 = 16 hard #4011: 8 _ 7 _ 4 _ 3 = 17 hard #4013: 8 _ 7 _ 4 _ 4 = 18 hard #4015: 8 _ 7 _ 4 _ 5 = 19 hard #4017: 8 _ 7 _ 4 _ 6 = 20 hard #4026: 8 _ 8 _ 2 _ 3 = 20 hard #4029: 8 _ 8 _ 2 _ 6 = 13 hard #4030: 8 _ 8 _ 2 _ 7 = 15 hard #4031: 8 _ 8 _ 2 _ 8 = 17 hard #4032: 8 _ 8 _ 2 _ 9 = 19 hard #4034: 8 _ 8 _ 2 _ 5 = -9 hard #4036: 8 _ 8 _ 3 _ 2 = 20 hard #4037: 8 _ 8 _ 3 _ 4 = 14 hard #4040: 8 _ 8 _ 3 _ 4 = 13 hard #4041: 8 _ 8 _ 3 _ 5 = 16 hard #4045: 8 _ 8 _ 4 _ 3 = 14 hard #4046: 8 _ 8 _ 4 _ 5 = 18 hard #4047: 8 _ 8 _ 4 _ 6 = 20 hard #4052: 8 _ 8 _ 4 _ 1 = 17 hard