= [ x^{3 }( 1 + x + x^{2 }+ x^{3 }+ ....................... ) ]^{3}
= x^{9 }( 1 + x + x^{2 }+ x^{3 }+.......................)^{3}
= x^{9 }(1 / ( 1 - x ) )^{3}
= x^{9 }( 1 / ( 1 - x )^{3 })
= x^{9 }( ( 1 - x )^{-3 })
= x^{9 }( 1 + (3)x + ( (3*4) / (1*2) ) x^{2 }+ ( (3*4*5) / (1*2*3) ) x^{3 }+...................................)
= x^{9 }+ 3x^{10 }+ 6x^{11 }+ 10x^{12 }+........................................................
Answer = 10