A crane lifts the 18,000 kg steel hull ship out of the water.
Volume of water displaced = Volume of submerged ship
Vw = (18,000 kg) / (7.8e^3 kg/m^3)
Vw = 2.3077 m^3
Weight of water displaced = (density of water)(volume of water)(acceleration due to gravity)
Ww = (1000 kg/m^3)(2.3077 m^3)(9.81 m/s^2)
Ww = 2.2638e4 N
By Archimedes’ principle, the buoyant force on the ship equals the amount of fluid displaced.
(Tension of cable) + (Weight of displaced water) = Weight of ship
T + 2.2638e4 N = (18,000 kg)(9.81 m/s^2)
T = 1.539e5 N
Your approach to this one is correct.