The rules are closed to the kakuro ones, but you have to take in account multiplications as well:
• for the additions the sign is “+”, for the multiplications the sign is “x”
• the arrows show the direction of the answers
?• digits 1 to 9 can be used, but in any answer a digit can only appear once.
Try to identify with the multiplications which are the possible factors. For example the 28(x) in three digits can only be 1x4x7, because the only other possibility (2x2x7) is not valid since it contains two times the same digit. But 36(x) in three digits can be 2x3x6 as well as 1x4x9.