I will also go with clubs with number 8.
Clubs is an appropriate option because spades, diamomds, hearts are 3 each whereas there ate only 2 clubs cards.
Number 8 because values of row1= 1 + row2 values (for e.g; in column 1 : 1+A= 2)
Row3= 1+ row2 (in column 1 : 1+2=3)