Linear inequalities in one or two variables SAT question

Choice B is correct. It's given that monarch butterflies can fly only with a body temperature of at least $55.0\text{degrees}\text{Fahrenheit}{(}^{\circ }\text{F})$. Let $x$ represent the minimum increase needed in the monarch butterfly's body temperature to fly. If the monarch butterfly's body temperature is $51.3^{\circ }\text{F}$, the inequality $51.3+x\ge 55.0$ represents this situation. Subtracting $51.3$ from both sides of this inequality yields $x\ge 3.7$. Therefore, if the monarch butterfly's body temperature is $51.3^{\circ }\text{F}$, the minimum increase needed in its body temperature, in ${}^{\circ }\text{F}$, so that it can fly is $3.7$.

Choice A is incorrect. This is the minimum increase needed in body temperature if the monarch butterfly's body temperature is ${\text{53.7}}^{\circ }\text{F}$, not $51.3^{\circ }\text{F}$.

Choice C is incorrect. This is the minimum increase needed in body temperature if the monarch butterfly's body temperature is $50.0^{\circ }\text{F}$, not $51.3^{\circ }\text{F}$.

Choice D is incorrect. This is the minimum increase needed in body temperature if the monarch butterfly's body temperature is $48.7^{\circ }\text{F}$, not $51.3^{\circ }\text{F}$.