Greetings, Shumeka.
Since the bike ride was longer than the bus ride -
Let x = KM of bus ride
Let x + 80 = KM of bicycle ride
We know the total of the trip was 350 KM, giving us
x + (x+80) = 350 (Note: the parentheses were added for readability)
Then 2x +80 = 350 and we solve for x (get it by itself).
Subtract both sides of the equation by 80 then divide both sides by 2.
We now have x, the bus ride, and we must add 80 to get the KM bicycled.