Adding the number of protons to the number of neutrons determines what about the atom? A
the atomic number
B
the atomic mass

(Hint: protons + neutrons = ?)

Number of protons is Z and number of neutrons is A-Z
The add the both
Z + A - Z
Z cancels to give A(Atomic mass)

"Pressure is the force which applied perpendicular to the surface."

P = F / A

Where P is pressure (N m⁻² ), F is force which is perpendicular to the surface (N) and A is area of the surface (m²).

Here,
The applied force into the input piston = 2000 N
The surface area of the input piston    = 200 cm² = 0.02 m²
Hence the pressure applied to input piston = 2000 N / 0.02 m²
                                                                     = 100000 N m⁻²

The force applied to the input piston acts on the liquid hydraulic system.

Hence the pressure on liquid = 100000 N m⁻²