SAT Question 1087f6c4: Linear Equations In Two Variables answer and explanation with Desmos solution

25. It’s given that the topsoil and crushed stone Isabel ordered for her garden cost a total of \641$.It’salsogiventhattheequation＄24.5x+24.75y=641$ represents the relationship between the number of cubic yards of topsoil, $x$, and the number of tons of crushed stone, $y$, that Isabel ordered. Since $x$ represents the number of cubic yards of topsoil ordered, ＄24.5 x represents the total cost, in dollars, of the topsoil, and the cost per cubic yard of topsoil is \24.50$.Similarly,since$y$representsthenumberoftonsofcrushedstoneordered,＄24.75y$ represents the total cost, in dollars, of crushed stone ordered, and the cost per ton of crushed stone is $24.75$.Therefore,atonofcrushedstonecostIsabel＄24.75-24.50$, or ＄0.25$, more dollars than a cubic yard of topsoil. Note that 1/4, .25, .250, and 0.25 are examples of ways to enter a correct answer.