we need first consider what data we have available: a = run 1.5km b = then run 2.3km c = walk 475m x = a + b + c = how many km he done on treadmill before we go anywhere, we need to unify the units, we need to change meters to fraction of kilometers, kilo meant 1000, therefore: 1km = 1000m 475m / 1000m = 0.475km now we can substitute: x = a + b + c = 1.5km + 2.3km + 0.475km = 4.275km we can round that up to first decimal point and then: 4.275km = 4.3km answer is then: jack done on the treadmill 4.275km or rounded up 4.3km