Despite best efforts, students in U.S. schools still underperform in mathematics compared to many other developed countries, and the achievement gap persists. Teachers play a most important role in student success, yet the knowledge about adult beliefs (and how they can be changed) concerning one's ability to learn math, the value one has for math, and one's understanding about how math anxiety derails learning still falls short in informing efforts to best train/support pre-service or in-service teachers. A group of undergraduate university students (N = 123) participated in a fully online intervention measuring each of the components in the Expectancy-Value-Cost (EVC) motivational model (Barron & Hulleman, 2015; Eccles & Wigfield, 2002; Wigfield & Eccles, 2000) as it related to their beliefs about mathematics, then completed a three-part intervention (based on Blackwell, Trzesniewski, & Dweck, 2007; Gaspard et al., 2015; and Ramirez & Beilock, 2011), followed by post-measurements of each of the components of EVC. Significant results were obtained for each component of EVC, implying short interventions can effect positive changes in beliefs for adults. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]