** Solving a Set of Equations by Search**

- Try to find an equation where all variables are known except one.
(= F (* M A))

- Solve the equation for that variable.
(= A (/ F M))

- Substitute the known values into the right-hand side of the solved
equation (Lisp function
`sublis`).(= A (/ 8 2))

- Evaluate the resulting expression (Lisp function
`eval`) to give the value of the new variable. Add that variable to the binding list.(= A 4)

- Keep trying until you get the value of the variable you want (or quit if you stop making any progress).