SAT Question e006209c: Linear Inequalities answer and explanation with Desmos solution

Choice C is correct. It's given that the geologist has already collected $63$ samples from the volcano. Let $x$ represent the number of additional samples the geologist needs to collect. After collecting $x$ additional samples, the geologist will have collected a total of $63+x$ samples. It's given that the geologist needs to collect at least $67$ samples. Therefore, $63+x\ge 67$. Subtracting $63$ from each side of this inequality yields the inequality $x\ge 4$. Thus, the geologist needs to collect a minimum of $4$ additional samples.