Answer:
fish: +10 N and -10 N
bottom of fish tank +70 N and -70 N
leg of the table +120 N and -120 N
Explanation:
arrow at the fish, downward: -10 N (down is negative, 10 N is the force exerted by the fish)
arrow at the fish, upward: +10 N (it must be in equilibrium with the previous one)
arrow at the bottom of the fish tank, downward: -70 N (down is negative, 70 is the addition of the forces exerted by the fish, 10 N, the aquarium, 20 N, and the water, 40 N)
arrow at the bottom of the fish tank, upward: +70 N (it must be in equilibrium with the previous one)
arrow at the leg of the table, downward: -120 N (down is negative, 120 is the addition of the forces exerted by the fish, 10 N, the aquarium, 20 N, the water, 40 N, and the table, 50 N)
arrow at the leg of the table, upward: +120 N (it must be in equilibrium with the previous one)
