Hard Arithmetic Puzzles

#535: 2 _ 2 _ 4 _ 9 = -8 hard #545: 2 _ 2 _ 6 _ 3 = 19 hard #546: 2 _ 2 _ 7 _ 2 = 15 hard #549: 2 _ 2 _ 8 _ 2 = 17 hard #555: 2 _ 2 _ 9 _ 2 = 19 hard #556: 2 _ 3 _ 2 _ 8 = 14 hard #567: 2 _ 3 _ 5 _ 6 = 20 hard #581: 2 _ 3 _ 6 _ 9 = -8 hard #586: 2 _ 3 _ 6 _ 5 = 20 hard #591: 2 _ 3 _ 6 _ 9 = 13 hard #596: 2 _ 3 _ 8 _ 2 = 14 hard #612: 2 _ 3 _ 9 _ 5 = 11 hard #613: 2 _ 3 _ 9 _ 6 = 12 hard #615: 2 _ 3 _ 9 _ 7 = 13 hard #617: 2 _ 3 _ 9 _ 8 = 14 hard #618: 2 _ 3 _ 9 _ 9 = 15 hard #623: 2 _ 4 _ 2 _ 7 = 16 hard #624: 2 _ 4 _ 2 _ 9 = 20 hard #642: 2 _ 4 _ 2 _ 9 = -8 hard #655: 2 _ 4 _ 5 _ 8 = 20 hard #671: 2 _ 4 _ 7 _ 2 = 16 hard #691: 2 _ 4 _ 8 _ 9 = -8 hard #698: 2 _ 4 _ 8 _ 5 = 20 hard #703: 2 _ 4 _ 8 _ 9 = 13 hard #705: 2 _ 4 _ 9 _ 2 = 20 hard #708: 2 _ 4 _ 9 _ 3 = 11 hard #712: 2 _ 5 _ 2 _ 6 = 17 hard #717: 2 _ 5 _ 3 _ 9 = 17 hard #722: 2 _ 5 _ 3 _ 6 = 20 hard #730: 2 _ 5 _ 4 _ 8 = 20 hard #733: 2 _ 5 _ 6 _ 2 = 17 hard #738: 2 _ 5 _ 6 _ 3 = 20 hard #741: 2 _ 5 _ 6 _ 9 = 15 hard #745: 2 _ 5 _ 8 _ 2 = 14 hard #750: 2 _ 5 _ 8 _ 4 = 20 hard #751: 2 _ 5 _ 9 _ 3 = 17 hard #752: 2 _ 5 _ 9 _ 9 = 11 hard #755: 2 _ 5 _ 9 _ 6 = 15 hard #757: 2 _ 6 _ 2 _ 5 = 17 hard #766: 2 _ 6 _ 3 _ 8 = 18 hard #784: 2 _ 6 _ 3 _ 9 = -8 hard #789: 2 _ 6 _ 4 _ 8 = 14 hard #813: 2 _ 6 _ 5 _ 2 = 17 hard #832: 2 _ 6 _ 8 _ 3 = 18 hard #835: 2 _ 6 _ 8 _ 2 = 16 hard #836: 2 _ 6 _ 8 _ 8 = 13 hard #844: 2 _ 6 _ 9 _ 3 = 15 hard #845: 2 _ 6 _ 9 _ 9 = 13 hard