GMAT Math questions are given to test your understanding of the mathematical concepts than to test your ability to actually carry out quantitative procedures correctly. These questions are simple but test-writers often complicate these problems by altering the sentences and concealing its structure and intent, while preserving its behavior. They usually do this to deceive the testers. Be careful in making assumptions that you are not supposed to make. It is impossible to overstate the importance of careful reading.
There are techniques that can be used to solve these problems and can also be found on GMAT preparation guides. One of which is by reading the question several times might help understand the question. Try to put it into your own words if not, break them into parts until you get the correct thought. Be careful with traps. Some numbers or words are usually added to confuse the reader.
Another technique is backsolving. This is done by substituting the answer choices to the given equation. For numerical answers, it is best to start with the middle choice then just go up or down based on the attempted result. Assume that the answer does not contain a variable and ensure that the numbers you chose don