"The fire in the Mission District was subdued with water found blocks away in a hydrant." is the sentence which uses a problem-solution structure.
In a sentence containing a problem-solution structure, you should be able to identify:
- an event which happened and can be considered a problem, in this case the fire which took place in the Mission District;
- what was done to fix to problem (the solution), in this case, bringing water from a fireplug a few blocks away.
What could help is to look for a "pivot verb" which serves as the transition from the problem to the solution. These are usually action verbs, like subdue in the text. Other examples could be fix, address, solve, respond to, etc.