mathematically,
[tex]pressure = \frac{force}{area} [/tex]
but weight= Force.
given pressure
18N/cm^2
and Force = 9000N
making area the subject in the relation above.
[tex]Area = \frac{force}{pressure} [/tex]
substitute their values into the equation
[tex]Area = \frac{9000}{18} [/tex]
[tex]Area = 500 {cm}^{2} [/tex]