Răspuns :
(64-32-12/k)-(40-20)=9
(32-12/k)-20=9
32-12/k=29
(32k-12)/k=29
32k-12=29k
32k-29k=12
3k=12
k=12/3
k=4
(32-12/k)-20=9
32-12/k=29
(32k-12)/k=29
32k-12=29k
32k-29k=12
3k=12
k=12/3
k=4