This study assessed the effectiveness of a three-step cognitive strategy (TIP) for calculating tip and total bill for young adults with intellectual disability. In the context of pre- and post-test nonequivalent-groups design, 10 students from a postsecondary education program for individuals with disabilities participated in the study. A teacher delivered six lessons to students in the experimental group using the working instructional model for teaching learning strategies. Results indicate that the experimental group outperformed the comparison group on items that assessed the ability to calculate tip and total bill. Students from the experimental group also generalized the procedural knowledge to tasks that required using percent values in different contexts. Four of the students from the experimental group maintained the use of the strategy 8 weeks after the intervention. (Contains 2 figures and 5 tables.)