\(a){\left( {3 + x} \right)^3} = {3^3} + {3.3^2}x + 3.3.{x^2} + {x^3} = 27 + 27{\rm{x}} + 9{{\rm{x}}^2} + {x^3}\)
\(b){\left( {a + 2b} \right)^3} = {a^3} + 3{{\rm{a}}^2}.\left( {2b} \right) + 3{\rm{a}}.{\left( {2b} \right)^2} + {\left( {2b} \right)^3} = {a^3} + 6{{\rm{a}}^2}b + 12{\rm{a}}{b^2} + 8{b^3}\)
\(c){\left( {2{\rm{x}} - y} \right)^3} = {\left( {2{\rm{x}}} \right)^3} - 3.{\left( {2{\rm{x}}} \right)^2}y + 3.2{\rm{x}}.{y^2} + {y^3} = 8{{\rm{x}}^3} - 12{{\rm{x}}^2}y + 6{\rm{x}}{y^2} + {y^3}\)