For everyone asking about how to do the ratio:
You do not require a mass to determine the ratio. Instead, you can derive the ratio by setting the torques of each side of the lever equal to each other such that τ(1)=τ(2). Then, rmgsinΘ=rmgsinΘ, and simplification yields r(1)m(1)=r(2)m(2), which can be rearranged to r(1)/r(2)=m(2)/m(1), where r(1) is the distance mass A is away from the fulcrum and r(2) is the distance mass B is away from the fulcrum. Simplifying r(1)/r(2) so the denominator equals 1 will yield the ratio m(2):m(1), and no further calculation is necessary.
Expanding on what you've said for compound machines.(And apologies for ms paint)
Let's say that we have a mass Y, and we're trying to figure out the mass R. This pictured lever are at equilibrium. As stated before, the main equation of levers is m1d1=m2d2.
The left lever is pushing upwards on the right lever at the point of contact.If we look at the left lever alone, what mass would need to be on the other side of the lever to have it at equilibrium? From the equation, we get m=Y*d1/d2.
The right lever is pushing downwards on the left lever at the point of contact. If we look at the right lever alone, what "mass" would need to be pushing upwards on the right lever? From the equation, we get n=R*d4/d3
Now, these two "masses" are equal (this comes from newtons third law, if we simply turn them into forces).so, we get that Y*d1/d2=R*d4/d3. Solving, the ratio Y/R=d4*d2/(d3*d1).
Now the best part of this equation is that d2 and d3 can be measured in advance, and you simply have to plug in your distances.
I'm pretty tired right now (school and stuff) so please correct me if I made a mistake.