Hard Arithmetic Puzzles

#3821: 8 _ 4 _ 7 _ 4 = 18 hard #3823: 8 _ 4 _ 7 _ 5 = 19 hard #3825: 8 _ 4 _ 7 _ 6 = 20 hard #3835: 8 _ 4 _ 8 _ 5 = 20 hard #3836: 8 _ 4 _ 8 _ 1 = 17 hard #3837: 8 _ 4 _ 8 _ 1 = 15 hard #3838: 8 _ 4 _ 8 _ 3 = 19 hard #3844: 8 _ 4 _ 9 _ 6 = 14 hard #3846: 8 _ 4 _ 9 _ 1 = 19 hard #3847: 8 _ 4 _ 9 _ 1 = 17 hard #3848: 8 _ 4 _ 9 _ 2 = 16 hard #3849: 8 _ 4 _ 9 _ 4 = 14 hard #3850: 8 _ 4 _ 9 _ 5 = 13 hard #3851: 8 _ 4 _ 9 _ 6 = 12 hard #3853: 8 _ 4 _ 9 _ 7 = 11 hard #3856: 8 _ 5 _ 2 _ 4 = 18 hard #3859: 8 _ 5 _ 2 _ 4 = 20 hard #3860: 8 _ 5 _ 2 _ 2 = 18 hard #3862: 8 _ 5 _ 2 _ 3 = 17 hard #3863: 8 _ 5 _ 2 _ 4 = 16 hard #3864: 8 _ 5 _ 2 _ 5 = 15 hard #3865: 8 _ 5 _ 2 _ 6 = 14 hard #3866: 8 _ 5 _ 2 _ 7 = 13 hard #3868: 8 _ 5 _ 2 _ 9 = 11 hard #3869: 8 _ 5 _ 3 _ 6 = 18 hard #3871: 8 _ 5 _ 3 _ 9 = -7 hard #3872: 8 _ 5 _ 3 _ 6 = 20 hard #3873: 8 _ 5 _ 4 _ 2 = 18 hard #3879: 8 _ 5 _ 4 _ 2 = 20 hard #3880: 8 _ 5 _ 4 _ 3 = 13 hard #3883: 8 _ 5 _ 4 _ 5 = 15 hard #3886: 8 _ 5 _ 4 _ 7 = 17 hard #3890: 8 _ 5 _ 6 _ 3 = 18 hard #3893: 8 _ 5 _ 6 _ 3 = 20 hard #3894: 8 _ 5 _ 8 _ 4 = 18 hard #3898: 8 _ 5 _ 8 _ 4 = 20 hard #3899: 8 _ 5 _ 9 _ 3 = -7 hard #3906: 8 _ 6 _ 2 _ 5 = 19 hard #3907: 8 _ 6 _ 2 _ 7 = 17 hard #3908: 8 _ 6 _ 2 _ 8 = 16 hard #3909: 8 _ 6 _ 2 _ 9 = 15 hard #3911: 8 _ 6 _ 3 _ 2 = 17 hard #3913: 8 _ 6 _ 3 _ 5 = 18 hard #3919: 8 _ 6 _ 3 _ 9 = 16 hard #3920: 8 _ 6 _ 3 _ 1 = 15 hard #3921: 8 _ 6 _ 3 _ 2 = 18 hard #3922: 8 _ 6 _ 3 _ 2 = 14 hard #3923: 8 _ 6 _ 3 _ 3 = 19 hard