Think about what it means if you have at most $24 to spend. Are you allowed to spend more than $24, exactly $24, or less than $24?

Which inequality symbol shows “or less”: $<$, $>$, $\le$, or $\ge$? Use that symbol to relate the total cost to $24.

In Desmos, you will use $x$ and $y$ instead of $s$ and $j$. Think of $x$ as the number of smoothies and $y$ as the number of juices. Rewrite each option by replacing $s$ with $x$ and $j$ with $y$.

For each answer choice, first take the corresponding equation (for example, change an inequality like $4x + 3y \le 24$ to the boundary line $4x + 3y = 24$) and type it into Desmos to see the line. Then change it to the inequality (such as $\le$, $\ge$, $<$, or $>$) so Desmos shades one side of the line.

Think about real possibilities, like buying no drinks, which is the point $(0,0)$ and costs $0. That point should be in the shaded region, because spending $0 is allowed when you have at most $24. The correct inequality will shade the side that includes $(0,0)$ and represents spending up to $24, not $24 or more.

Each smoothie costs $4 and there are $s$ smoothies, so smoothies cost $4s$ dollars total.

Each juice costs $3 and there are $j$ juices, so juices cost $3j$ dollars total.

So the total amount of money the customer spends is represented by the expression $4s + 3j$.

“At most $24” means the customer can spend $24 or less, but not more than $24.

In inequality symbols, “$24 or less” is written using the less than or equal to sign: $\le$.

We want to show that the total cost $4s + 3j$ must be no more than $24.

So we write the inequality

Now compare this with the choices: this matches choice C, $4s + 3j \le 24$. This is the correct answer.