b + 4b = 8
You have to combine the like terms and then divide both sides by the coefficient to isolate the variable b.
b + 4b = 8
5b = 8
(5b / 5) = 8 / 5
b = 1.6
Since it says to round to the nearest hundredth, I would just put a zero right after the tenths place.
b = 1.60