w = weight of 1 cup
b = weight of empty bottle
2w + b = 360
5w + b = 600
Can you solve it from here?
Hint: start by subtracting the 2 equations.
=^._.^=
2 cups + bottle = 360
5 cups + bottle = 600
3 cups of water = 1/3(600 - 360)
1 cup of water = 80 grams
Weight of bottle = 360 - 160 = 200 grams
Mass of 3 cups water = 600 g - 360 g = 240 g
Mass of 5 cups water = 240 g * 5 cups / 3 cups = 400 g
Mass bottle + 5 cups water = 600 g
Mass 5 cups water = 400 g
Mass of bottle = 200 g