Answer:
0.7 kg
Explanation:
x = mass of the empty container (just the container alone)
y = mass of the sand in the full container.
x + y = 1.26 kg
x + 5/8 × y = 1.05 kg
=>
x = 1.26 - y
(1.26 - y) + 5y/8 = 1.05
8×(1.26 -y) + 5y = 8×1.05
8×1.26 - 8y + 5y = 8×1.05
10.08 - 3y = 8.4
3y = 1.68
y = 0.56 kg
x = 1.26 - 0.56 = 0.7 kg