# Using a linear regression equation, how can I interpolate the value of X when I have a specific value for Y?

From the linear regression equation $Y = M X + C$, where $M$ is the gradient or slope of the least squares line and $C$ is the y-intercept of the least squares line, you may find the X-value by making use of the inverse function to obtain that
$X = \frac{Y - C}{M}$