Research studies have shown that students encounter difficulties in transitioning from arithmetic to algebra. Errors made by high school students were analyzed for patterns and their causes. The origins of errors were: intuitive assumptions, failure to understand the syntax of algebra, analogies with other familiar symbol systems such as the English alphabet and interference from arithmetic. There were other psychological factors such as carelessness, anxiety, overconfidence, and lack of motivation. Three major error types are discussed with their causes using a cognitive psychological approach. Solution methods of another group of students show that they were eager to use algebraic methods over arithmetic procedures even though arithmetic procedures are more straightforward. The paper argues that creative methods used by some students should be used to reinforce the learning of other students.