SAT Question 174885f8: Linear Equations In Two Variables answer and explanation with Desmos solution

Choice A is correct. Since Jay walks at a speed of $3$ miles per hour for $w$ hours, Jay walks a total of $3w$ miles. Since Jay runs at a speed of $5$ miles per hour for $r$ hours, Jay runs a total of $5r$ miles. Therefore, the total number of miles Jay travels can be represented by $3w+5r$. Since the combined total number of miles is $14$, the equation $3w+5r=14$ represents this situation.