Question 173235
d = r * t, so r = d / t


"Mike made a trip in 40 hours" __ r = d / 40


"Joe made the same trip in 30 hours because Joe was traveling 6km per hour faster" __ r + 6 = d / 30


substituting __ (d/40)+6 = d/30


multiplying by 120 (LCD) __ 3d + 720 = 4d


subtracting 3d __ 720 = d