SAT Question 535fa6e6: Linear Equations In Two Variables answer and explanation with Desmos solution

Choice D is correct. Let $p$ represent the number of pounds of potatoes and let $c$ represent the number of pounds of celery that Davio bought. It's given that potatoes cost $$0.69$ per pound and celery costs $$0.99$ per pound. If Davio spent $$5.34$ in total, then the equation $0.69p+0.99c=5.34$ represents this situation. It's also given that Davio bought twice as many pounds of celery as pounds of potatoes; therefore, $c=2p$. Substituting $2p$ for $c$ in the equation $0.69p+0.99c=5.34$ yields $0.69p+0.99\left(2p\right)=5.34$, which is equivalent to $0.69p+1.98p=5.34$, or $2.67p=5.34$. Dividing both sides of this equation by $2.67$ yields $p=2$. Substituting $2$ for $p$ in the equation $c=2p$ yields $c=2\left(2\right)$, or $c=4$. Therefore, Davio bought $4$ pounds of celery.