From 1st principle find the derivative of log (ax+b)

Step-by-step explanation:

The parent function here is y = log x, where 10 is the base.

The derivative of y = log x is dy/dx = (ln x) / ln 10.

The derivative of y = log (ax+b) is found in that manner, but additional steps are necessary:  differentiate the argument ax + b:

The derivative with respect to 10 of log (ax + b) is:

dy/dx = [ 1 / (ax + b) ] / [ ln 10 ] *a, where a is the derivative of (ax + b).

Alternatively, we could express the answer as

dy/dx = [ a / (ax + b) ] / [ ln 10 ]

i assume that by 5 you mean 5 gallons.

(20)(0.25) = 15

removing 15 gallons reduces the tank from 20 to 5.