Going down 250 feet will mean going down feet 250 so it will be -250. Rising 80 feet will mean going up 80 feet so it will be adding 80. Finally, descending 18 feet will mean going down 18 feet, so it will be -18. If you put them all together as one equation, you will get -250 + 80 - 18 which is -118.
Step-by-step explanation: the submarine starts at sea level, goes down 250 feet (-250). rises 80 feet (-170). descends 18 feet (-188). i don't know if this is correct or not. i haven't learned descending yet so idk- i think it's right i'm not sure. i don't know if this is right i'm so sorry.
It does not matter which color you add first because either way you will end up with the same color, purple. We can relate this to the commutative property of addition because blue + red = red + blue.