I wish to solve this euqtion to find LC 90 .
I need to figure out the value of concentration which would kill 90% of toxic material.
The value of a,b,c,d is known from regression .
I need to cut down the quation to find con value.
10%=Exp^(a*con+b)+Exp^(c*con+d) which should give me
Could any body help me solve this equation.