2 7/8 is not an integer value, so cannot be expressed as an integer.
It can be rounded to the nearest integer, 3.
Step one, divide both sides by -2
log8(x+1)=4
if the base is 10, and the 8 is together with (x+1): (cannot tell from the way it is written)
8(x+1)=10^4=10000
x+1=1250
x=1249
if the 8 is a base,
8^4=(x+1)
x+1=4096
x=4095
The answer really depends on what b is. Unless you give me a number for what b equals I can’t solve it.