I am setting up a calibration curve, where x= concentration and y=
absorbance. The curve is polynomial.

after plotting x and y values using a scattergraph and applying a trend
line, i got the following regression line:
y= -0.0881x^2+2.8089x+0.0505.

If the absorbance reading (y) = 0.212, how do I calculate the value of x?

Thanks in advance