This text is all about percentages, a common measure of performance in diverse settings. Working with percentages is an important element of the PSAT/SAT Math test which includes multi-step applications that use ratios, percentages, and proportional reasoning to solve problems in science, social science, and other real-life situations. When do students practice these skills? This book contains fifteen scenarios where students analyze, solve problems, make decisions and model situations mathematically. The scenarios include stepping stones to Algebra where students transition from percentages to writing expressions involving a variable, to solving simple algebraic equations. Each scenario requires the habits of mind supported in the mathematical practices: persevering, constructing viable arguments, reasoning abstractly and quantitatively, and modeling with mathematics.