What are the possible ways to solve 2 unknowns in 3 equations?

I have 3 eqns and 2 unknowns Hb and Hbo2, they

look like this: Bxy = AB * HB + AB * Hbo2 Rxy = AR * HB + AR * Hbo2 Gxy = AG * HB + AG * Hbo2 Now I have been trying to use a matrix method in

order to solve the unknowns for them equations,

which is a pain in the *** cause when I convert it to

matrix form I get an irregular matrix because it is 2

unknowns and 3 equations. Does anyone on here know how to solve n number

of equations with n-1 unknowns. EDIT Thanks for the responses so far, they have been

great. To help make this more clear, what I am trying to

do is work out the concentration of oxygenated

and deoxygenated blood at a given pixel in an

image. so the variables above correspond to the

following. Rxy Gxy and Bxy, red green or blue absorbed at

position x,y. (value between 0 - 255) AR, AG, AB is the absorption coefficient of light for

Red geen and blue wavelengths for blood.

(HOWEVER there is a possibility I might have to

define different absorption coefficients for

oxygenated and deoxygenated blood (as they

absorb different amounts of light)). Hb and Hbo2 is the concentration of Oxygenated

and Deoxygenated blood. (these are unknown as

I'm trying to map the RGB values to this) However I have also noticed that the coefficients for

Oxygenated and Deoxygenated blood are different

so this means the equation could possibly be the

following. Bxy = (ABhb * HB) + (ABhbo2 * Hbo2) Rxy = (ARhb * HB) + (ARhbo2 * Hbo2) Gxy = (AGhb * HB) + (AGhbo2 * Hbo2) The only difference in the above is that the

coefficients are different for oxygenated and

deoxygenated blood