Hi Jlim (and Nick and Youtthasack)
I just want to respond quickly to jLim's question. Yes, you are right. That's one way to write a problem solution essay.
OK, most problem/solution essays will have an intro, a paragraph with the problems, a paragraph with the solutions, and a conclusion. That's what Nick did in the first essay in this post, and it's absolutely fine. You can see two other essays with this format here and here (both on why people drop out of school early).
Another way is to write an intro, then problem and its solution, a second problem and its solution, and a third problem and its solution, followed by a conclusion. This will result in a 35553 essay (3-sentence intro, 5 sentences in each of the body paragraphs, and a 3-sentence conclusion).
But be careful jLim not to have too many ideas and too many solutions. Three is enough. Find three aspect of the problem, and suggest three solutions. You will have to write five sentences approximately on each idea.
Here's an example from Nick's topic. It's one ONE body paragraph - you would need two more.
Another problem caused by rapid development is loss of land. As cities grow, they swallow up huge areas around them. These areas are often fertile areas which were previously used for agriculture. This places pressure on the people who lived there previously - their lives are changed forever, and the food which they used to grow is no longer available. This problem is difficult to solve, but governments need to control the rate of expansion of cities. One answer is to build more high-rise apartments. Another is to develop new towns and cities in areas which are less suitable for agriculture.
100 words, seven sentences (oops!) and 14 words per sentence average. It's a bit long but you get the idea: a problem with some more information, followed by one or two solutions.
You need two more paragraphs like this (though shorter, please!) and an intro and conclusion.
So basically, yes, jLim is correct. But don't just write one sentence problem, one sentence solution. Develop your ideas.