Faucet A fills a sink in 2 hrs. Faucet A and B fill the same sink (together) in 1 hr 15 mins. Faucet B would take how long to fill the sink by itself?" (Faucet B is slower)
1/A + 1/B = 1/C
1/2 + 1/B = 1/1.25
Now just figure B.
1/2 + 1/B = 1/1.25
Now just figure B.