Steps:
1) Group the like terms and simplify.
2) Do follow the BODMAS Rule. Simplify terms inside the brackets, first. Then, follow this serial: Division, Multiplication, Addition, Subtraction.
Method:
\((2u^3 + 6u^2 + 3) + (2u^3 - 7u + 6)\)
= \(2u^3 + 6u^2 + 3 + 2u^3 - 7u + 6\)
= \(2u^3+2u^3+6u^2-7u+3+6\)
= \((2u^3+2u^3)+6u^2-7u+(3+6)\)
= \(4u^3+6u^2-7u+9\)
