Use the rule of Logarithm, then solve for x

Log 2x+1 - log (x+5)=0
x=4

*I know x equals for can you explain how?

I think you mean

log(2x+1) = log(x+5)
The terms in parenteses must be equal if their logs are equal, so
2x + 1 = x + 5
x = 4