Look up the mass of titanium.

Calculate the mass of 3.05 ×10^23 atoms of titanium.

Divide by 4.50 g/cm^3 to find the volume of the cube.

Do some basic geometry to find the length of the edge.

1 mole contains 6.02 x 10²³ atoms

(3.05 x 10²³) / (6.02 x 10²³) = 0.507 mole

Atomic mass of titanium = 47.867g/mole

47.867g/mole * 0.507 mole = 24.27 grams

24.27 grams * 1cm³/4.50g = 5.39 cm³

³√(5.39 cm³) = 1.81cm

Edge length is 1.81 cm <––––––