The problem: someone has a fatal tumor embedded in their spleen such that physical surgery is impossible because the tumor is too nestled in with the other organs. The problem is solved if you can kill the tumor without killing the patient.
You have the technology to build a laser gun that kills tumors. The laser gun has ten power settings (setting 1=10% power, setting 2 = 20%, etc. up to level 10 = 100% which is full power.) The laser gun only slows the tumor growth on settings 1-9. It successfully kills the tumor at 10, but that also blasts through the tumor and kills the patient due to the surrounding tissue damage.
The problem: How can you utilize this technology, as stated to kill the tumor but not kill the patient?