Whats‘up？Chemistry?

W is deposited on the cathode. This can be deduced that the ion of W is a cation which carries positive changes.

Wⁿ⁺(aq) + ne⁻ → W(s)

Each mole of e⁻ carries 1 F of electricity.
No. of moles of e⁻ = (2F) / (1 F/mol) = 2 mol

Molar mass of W = 45 g/mol
No. of moles of W = (30 g) / (45 g/mol) = 2/3 mol

Mole ratio e⁻ : W
n : 1 = (2 mol) : (2/3 mol)
(2/3)n = 2
n = 2 × (3/2)
n = 3

Ionic formula of the ion of W = W³⁺