When trying to solve questions involving fractions/percentages of unknown numbers (“1/3 of the class are 10th grade boys… what fraction of the class are ninth graders?”), don’t put together any equations with variables: Just assign an easy-to-work-with number for the unknown, and work out the details to figure out what you’re looking for. Just be sure to select small numbers that divide up nicely with the fractions/percentages you’re given.
You can also use this technique when asked to alter algebraic expressions around—just select actual numbers for the variables in the question, and see which answers line up when you plug in those same numbers.
SAT Prep Plan: SAT Tips 
