Easier (usually) KenKen's have symbols in them. This one doesn't and you have to figure it out. Some are obvious, such as 2 spaces for 42. Those have to be 6 and 7, although you do not yet know which order. Others, such as 12 can be either additional or multiplication, or something like 4 could be division (8 / 2, 4 / 1), multiplication (4 * 1), addition (1 + 3), or subtraction (9 - 5, 8 - 4, 7 - 3, 6 - 2, 5 - 1). Fortunately, in this case, both divisions are the same numbers as other operations, so you can assume multiplication, addition, or subtraction.