Trouble finding the R(equivalent) in this circuit
Your book is wrong, and you are right:







simulate this circuit &ndash; Schematic created using CircuitLab

Try to simulate that, and you will get that the voltage across the current generator is 30V, i.e. the resistance seen by the current generator is \$\frac{30}{1}\Omega=30\Omega\$.

This trick is very useful when you have tons of exercises with no solution, plus you learn how to use a simulator (use some spice flavour). Of course you should always solve the exercise by hand and, if you are not sure your result is correct, check it with the simulator. Learning how to deal with circuits without the help of a computer is a necessary base for an EE, don't be too attracted by the simulator.