Question

The answer in decimal

Answer 1

Apply the common log function to both sides of this equation to solve it:

x log 10 = (x+3) log 5  = x log 5 + 3 log 5

Group the x terms together on the left:   x (log 10 - log 5) = 3 log 5

Simplify the quantity inside the parentheses:  log 10 - log 5 = log 10/5 = log 2.

Then x log 2 = 3 log 5.  Solving for x:  (3 log 5) / (log 2)    (answer)