In a message dated 02/27/2000 9:35:47 PM Eastern Standard Time, noahd@juno.com writes: << 5=12*(1-e^((-1.3E-6)/x)) For x, using "solve(5=12*(1-e^((-1.3E-6)/x)),x)" I get x = 0 >> hmm, x=0 when the last part is [a]/x. dividing by zero, that could be a problem. my 89 doesnt seem to like me, so dont ask me