In this case, according to the given information, it turns out firstly necessary for us to set the equation for the calculation of density and mass divided by volume:
Thus, we can find the mass of the unknown by subtracting the total mass of the liquid to the mass of the flask and the liquid:
So that we are now able to calculate the density in g/mL first:
Now, we proceed to the conversion to lb/in³ by using the following setup: