You have the following expression:
(2x + 5) + (3x² + 7x + 3)
in order to somplify the previous expression, consider that like terms are term with the same varibale and same exponents. Like terms are the terms you can simplify.
Then, proceed as follow:
(2x + 5) + (3x² + 7x + 3) cancel out parenthesis
2x + 5 + 3x² + 7x + 3 order like terms
3x² + 2x + 7x + 5 + 3 simplify like terms (2x and 7x, 5 and 3)
3x² + 9x + 8
Hence, the simplified expression is: