The world's supply of helium is finite. There are approximately 35 billion cubic meters of helium on Earth, and every year humans consume about 210 million cubic meters of it. Let stand for the volume (in millions of cubic meters) of helium remaining, and stand for the number of years since 2018. Which of the following linear equations could model the decreasing supply of helium

It follows from the task content that the equation which correctly models the decreasing supply of helium according to the description is to be determined.

Let, y = amount of helium remaining.

Let x = no of years since 2018.

First, one must convert 210 million to billion cubic feets as follows;

210 million = (210/1000) billion.

= 0.21 billion cubic meters per year.

The number above represents the rate of change of the linear model, otherwise termed the slope.

On this note, since the starting deposit of helium in 2018 was; 35 billion.

This insinuates that the y-coordinate of the y-intercept of the required model is; 35.

Hence, the required decreasing Linear model for the supply of helium is;

y = 35 - 0.21x.

The equation above follows from the slope-intercept form of a linear equation.