Explain according to which law the force of gravity acting on a body is equal

Explain according to which law the force of gravity acting on a body is equal to the product of the mass of this body and the acceleration of gravity.

From Newton’s second law and the law of gravitation.
From Newton’s second law, we have that F (force) = m (body mass) * a (acceleration), which implies that F m. (Gravity) = m (body mass) * g (some acceleration) ( 1 formula)
From the law of universal gravitation we have that F t. (Gravity) = G (gravitational constant) * M (planet’s mass) * m (body mass) / R ^ 2 (planet’s radius). Let’s take the body weight forward, and equate the resulting expression and formula 1, we get that m * g = m * G * M / R ^ 2, whence we get that g = G * M / R ^ 2, i.e. g is the acceleration of gravity, which means gravity = body mass * acceleration of gravity.