Can you do some algebra to separate out the factors of Vi in each term on the right-hand side?
You might want to take care in using parenthesis around (ViCos30), especially in the second term on the right-hand side.
Let's go slowly... do algebra first (arithmetic last). It's easier to spot an algebra mistake.
Can you factor "(ViSin30)10 * ViCos30" ?
It may help to forget the numbers and think of this symbolically as [tex](V_i A)B * V_iC[/tex]. So, can you factor this expression and write it in terms of [tex]V_i[/tex], [tex]A[/tex], [tex]B[/tex], and [tex]C[/tex]?