URGENT Problem
A student places a steak on one side of a double balance pan. She adds weights of known mass to the other side until both sides are balanced.
Then, she eats three fourths of the steak and places it back on the scale.

Figure 1: Double balance pan. Image from Wikimedia Commons, CC0 1.0.
How can she find gravitational mass of the steak ?
Assume all the weights of known mass are equal.