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)
