Sea level is 0
robert dives 40 ft.....-40
he then rises 23 ft.....-40 + 23 = -17
he then dives 19 ft to meet Sam....-17 - 19 = -36
together they rise 31 ft...-36 + 31 = - 5
they are 5 ft below sea level <==
8(8 + X) = 16
64 + X = 16
-64 -64
X = -48
13km i think / that maybe wrong too
