Arithmetic Operator Puzzles

#1537: 3 _ 9 _ 6 _ 3 = 6 easy #1538: 3 _ 9 _ 6 _ 4 = 6 medium #1539: 3 _ 9 _ 6 _ 4 = -2 medium #1540: 3 _ 9 _ 6 _ 4 = 8 easy #1541: 3 _ 9 _ 6 _ 5 = 7 medium #1542: 3 _ 9 _ 6 _ 5 = 10 medium #1543: 3 _ 9 _ 6 _ 6 = 8 medium #1544: 3 _ 9 _ 6 _ 6 = -4 medium #1545: 3 _ 9 _ 6 _ 7 = 9 medium #1546: 3 _ 9 _ 6 _ 8 = -6 medium #1547: 3 _ 9 _ 6 _ 8 = 16 hard #1548: 3 _ 9 _ 6 _ 9 = 11 hard #1549: 3 _ 9 _ 6 _ 9 = -7 hard #1550: 3 _ 9 _ 8 _ 6 = 15 hard #1551: 3 _ 9 _ 8 _ 6 = -9 hard #1552: 3 _ 9 _ 8 _ 3 = 8 easy #1553: 3 _ 9 _ 8 _ 6 = 16 hard #1554: 4 _ 1 _ 2 _ 8 = 8 medium #1555: 4 _ 1 _ 3 _ 9 = 7 medium #1556: 4 _ 1 _ 3 _ 9 = 1 easy #1557: 4 _ 1 _ 4 _ 8 = 6 easy #1558: 4 _ 2 _ 2 _ 4 = 3 easy #1559: 4 _ 2 _ 2 _ 2 = 9 easy #1560: 4 _ 2 _ 3 _ 6 = 8 easy #1561: 4 _ 2 _ 3 _ 9 = 10 medium #1562: 4 _ 2 _ 3 _ 9 = -2 medium #1563: 4 _ 2 _ 3 _ 1 = 7 easy #1564: 4 _ 2 _ 3 _ 2 = 4 easy #1565: 4 _ 2 _ 3 _ 3 = 18 easy #1566: 4 _ 2 _ 3 _ 4 = 10 easy #1567: 4 _ 2 _ 3 _ 5 = 11 easy #1568: 4 _ 2 _ 3 _ 5 = 1 easy #1569: 4 _ 2 _ 3 _ 6 = 12 medium #1570: 4 _ 2 _ 3 _ 6 = 1 easy #1571: 4 _ 2 _ 3 _ 7 = 13 medium #1572: 4 _ 2 _ 3 _ 7 = -1 easy #1573: 4 _ 2 _ 3 _ 8 = 14 hard #1574: 4 _ 2 _ 3 _ 8 = -2 easy #1575: 4 _ 2 _ 3 _ 9 = -3 medium #1576: 4 _ 2 _ 3 _ 9 = 6 easy #1577: 4 _ 2 _ 4 _ 8 = 5 easy #1578: 4 _ 2 _ 4 _ 2 = 5 easy #1579: 4 _ 2 _ 4 _ 6 = 7 easy #1580: 4 _ 2 _ 4 _ 8 = 8 medium #1581: 4 _ 2 _ 4 _ 8 = 3 easy #1582: 4 _ 2 _ 4 _ 2 = 3 easy #1583: 4 _ 2 _ 4 _ 6 = 1 easy #1584: 4 _ 2 _ 4 _ 4 = 9 easy