WeBWorK is a system that allows professors to put the homework problems on the web and allows you to solve these problems over the web. Using WeBWorK, you may try to answer homework problems more than once. After each try, a message appears telling you whether the answer is correct or not. This allows you to try to find out what they did wrong and hopefully to understand the topic of the question better.
Each WeBWorK problem set is individualized (each student has a different version of each problem, for example the numerical values in the formulas may be slightly different).
