Divide each term in by .

Cancel the common factor of and .

Factor out of .

Cancel the common factors.

Factor out of .

Cancel the common factor.

Rewrite the expression.

Reduce by cancelling the common factors.

Convert the exponential equation to a logarithmic equation using the logarithm base of the right side equals the exponent .

Convert to Logarithmic Form 400/(900-e^(x/9))=80