Explanation:

- To find the length of each side of the cube, we use the formula for the total surface area of a cube: $6s^2$, where $s$ is the side length.

- Given: Total surface area = 1350 cm${}^2$.

- Equation: $6s^2=1350$.

- Solving for $s^2$, we get $s^2=225$.

- Finding $s$ by taking the square root: $s=15\text{ cm}$.

Options:

- Option 1: 21 cm

- Option 2: 20 cm

- Option 3: 15 cm

- Option 4: 18 cm