How do you solve this logarithmic equation 3x plus 7 equals 20?

Answer 1

To be logarithmic the equation would be, ( otherwise just linear )

3x + 7 = 20

subtract 7 from each side

3x = 13

now, you know the answer is between x = 2 and x = 3, so I use natural logs both sides

ln(3x) = ln(13)

as this is a logarithmic operation you can bring down the x in front of the ln sign on the left

x ln(3) = ln(13)

divideboth sides by ln(3)

x = ln(13)/ln(3) ( not ln(13/3)!!!!! )

x = 2.334717519

-------------------------check in original equation

3(2.334717519) + 7 = 20

13 + 7 = 20

20 = 20

--------------checks