SAT Question 5805e747: Equivalent Expressions answer and explanation with Desmos solution

Choice A is correct. Applying the distributive property, the given expression can be written as $7x^3+7x-6x^3+3x$. Grouping like terms in this expression yields $\left(7x^3-6x^3\right)+\left(7x+3x\right)$. Combining like terms in this expression yields $x^3+10x$.