Problem - solution is a very common text pattern. You see it all the time. It's often used in advertising: "Do you have this problem? We (or this product) can solve it for you".
In many texts the words "problem" and "solution" are not actually mentioned. It's expected that the reader will understand that it is a problem which is being described. Often the solution is is not explicitly signalled either (although it is in the example below).
Problem - Solution
"It’s typical – you’re waiting at a bus stop for ages, then three buses come along at once. Should you just hop on the first one, or skip to the second or third? Various tech companies are trying to produce apps to help commuters plan for this type of event. But until those are up and running, some basic knowledge of the transport system – and a bit of mathematics – can help you make the call.
Studies have actually proven that buses which run at short intervals often cluster in threes. The theory goes that when there’s been a delay, the first bus picks up all the waiting passengers: those who have been waiting for some time, and those who have only been there a few minutes and had planned to get a slightly later bus.
This brings about further delays, because – as we all know – more congested vehicles take longer to load and unload. So the first bus often gets caught in a vicious circle of delay and overcrowding.
The simple solution is to get on the second bus. It’s likely to be less crowded, and to arrive at its destination first. This is because bus operators often instruct the second bus to overtake the first, in order to minimise delays.” (Bamford /& Mayers, n.d.)
The following text is an example of a problem-solution format. It is taken from an article in "The Conversation” by Marcus Mayers and David Bamford from the University of Huddersfield, and you can access the full article here. Mouse over the page to see how this text is structured.
This is a pointer to the solution (basic knowledge of the transport system and some mathamatics), but we still don't know what the actual solution is.
Bamford, D., /& Mayers, M. (n.d.). Transport experts explain why buses come in threes – and which one you should get on. Retrieved August 24, 2019, from The Conversation website: http://theconversation.com/transport-experts-explain-why-buses-come-in-threes-and-which-one-you-should-get-on-99348
The last two sentences give an explanation as to why this solution (getting on the second bus) is likely to work.
This is the problem: the problem of choosing which bus to take when there are three to choose from. The first, the second, or the third? Notice that the problem is not signalled. It doesn't say "The problem is ....". This is true of many texts.
These two short paragraphs give some background information and an explanation of why buses often arrive in threes. This leads us to a solution.
Transport experts explain why buses come in threes – and which one you should get on
This could be a solution but it’s not ready yet (or at least it wasn’t when this article was written).
Here we have the solution. Unlike the problem, it’s clearly signalled: "The simple solution is .."