8 = 5 + 2log(x/4)
First, I like to put the log on the left side, so switch the sides.
5 + 2log(x/4) = 8
Subtract 5 from each side
2log(x/4) = 3
Divide both sides by 2
log(x/4) = 3/2
When using logs, one of the rules is that x = logy(y^x). Apply this. Use 10 for y because by default log uses 10. Use 3/2 for x.
3/2 = log10(10^3/2) = log10(10[tex] \sqrt{10} [/tex])
Now we have log10(x/4) = log10(10[tex] \sqrt{10} [/tex])
Both have the same log base, so eliminate the logs.
x/4 = 10[tex] \sqrt{10} [/tex]
Multiply everything by 4 to get x by itself
x = 40[tex] \sqrt{10} [/tex]
