A large share of SAT system questions arrive as a short story about tickets, snacks, or work hours. Two unknown quantities, two facts about them. The math after setup is routine, so almost all the difficulty lives in translating the sentences into equations and in reading what the final line actually asks for.
Nearly every SAT setup follows the same shape. One sentence counts things and one sentence totals something those things carry, usually money or weight or time. If a store sells 40 items in total made of small boxes and large boxes, that is your count equation: s plus l equals 40. If small boxes cost 3 dollars and large boxes cost 7 dollars and the total was 200 dollars, that is your value equation: 3s plus 7l equals 200.
Define your variables in writing before you do anything else, including the unit. Writing s equals number of small boxes takes two seconds and prevents the most common setup error, which is letting a letter mean the money from small boxes in one equation and the count of them in the other. Once the letters are pinned down, each sentence usually converts directly into one equation.
Solve the count equation for one variable and substitute, since it almost always has coefficients of 1. From s plus l equals 40 you get s equals 40 minus l. Substituting into 3s plus 7l equals 200 gives 120 minus 3l plus 7l equals 200, so 4l equals 80 and l equals 20. Then s equals 20 as well. The arithmetic is short because you picked the easy equation to isolate.
Now read the last line of the question again. It might want the number of large boxes, or the number of small boxes, or the difference between them, or the amount of money the small boxes brought in. These are four different numbers built from the same solution, and the wrong ones are always sitting in the answer choices. Circle the requested quantity before you solve so you do not stop one step early.
Watch for constraints that are not equations at all. Phrases like at least or no more than turn the problem into a system of inequalities rather than equations, and the answer becomes a region or a maximum count instead of a single point. Also keep an eye on units: if one rate is given per hour and a total is given in minutes, convert before you write the second equation.