What is the weight of the load suspended on a spring with a stiffness of 900 N / m, if the spring is stretched by 3 cm?

According to Newton’s third law, the spring force will be balanced by the force of gravity.
Fcont. = Fт., Where Fcont. = k * ∆l (k is the stiffness of the spring, k = 900 N / m, ∆l = the amount of deformation, ∆l = 3 cm = 0.03 m), Ft = m * g (m is the mass of the load, kg, g – acceleration of gravity (we take g = 9.8 m / s ^ 2)).
Then:
k * ∆l = m * g.
Let’s express the mass of the cargo:
m = k * ∆l / g = 900 * 0.03 / 9.8 = 2.76 kg.
Check: kg = (N / m) * m / (m / s ^ 2) = N / (m / s ^ 2) = (kg * m / s ^ 2) / (m / s ^ 2) = kg.
Answer. The weight of the cargo is 2.76 kg.