You should now have an expression like $12t + 4p$ for the total money. Next, decide what inequality symbol to use to compare this expression to 300.

Does “at least $300” mean less than 300, more than 300, equal to 300, or 300 or more? Which inequality symbol matches that meaning?

In Desmos, use $x$ for $t$ (T-shirts) and $y$ for $p$ (posters). For each answer choice, replace $t$ with $x$ and $p$ with $y$ and type the inequality exactly as written, such as 12x + 4y >= 300 or 12x + 4y <= 300.

Think of a combination that clearly raises exactly $300, for example 25 T-shirts and 0 posters (since $12 \cdot 25 = 300$). In Desmos, type this as the point (25, 0) and see whether it lies on the boundary line or in the shaded region for each inequality. That shows whether the inequality allows a combination that exactly meets the goal.

Now test a combination that raises more than $300, such as 30 T-shirts and 0 posters (since $12 \cdot 30 = 360$). Plot (30, 0) and check which inequalities shade this point. The correct inequality will include both the point that makes $300 and points that make more than $300.

Each T-shirt brings in $12 and there are $t$ T-shirts, so money from shirts is $12t$.

Each poster brings in $4 and there are $p$ posters, so money from posters is $4p$.

Add these to get the total amount of money raised:

The phrase “at least $300” means the total can be 300 or more.

Mathematically, “at least” becomes the inequality symbol $\ge$ (greater than or equal to).

So we set the total money expression from Step 1 to be greater than or equal to 300:

This inequality matches answer choice A) $12t + 4p \ge 300$.