6. (a) \( 2 x^{2}+2 x+3 x^{2}+5 x \) (b) \( 3 m^{2}+2 m+4 m^{2}-3 m \) (c) \( -8 q^{2}-3+4 q^{2}-q \)

To simplify the expressions, we combine like terms by adding the coefficients of terms that share the same variable and exponent. For the first expression, \( 2x^2 + 2x + 3x^2 + 5x \), we combine the \( x^2 \) terms: \( 2x^2 + 3x^2 = 5x^2 \). Then, we combine the \( x \) terms: \( 2x + 5x = 7x \). Thus, the simplified expression is \( 5x^2 + 7x \). For the second expression, \( 3m^2 + 2m + 4m^2 - 3m \), we first combine the \( m^2 \) terms: \( 3m^2 + 4m^2 = 7m^2 \). Next, we combine the \( m \) terms: \( 2m - 3m = -m \). So, the simplified expression becomes \( 7m^2 - m \). In the last expression, \( -8q^2 - 3 + 4q^2 - q \), we start with the \( q^2 \) terms: \( -8q^2 + 4q^2 = -4q^2 \). The linear term \( -q \) remains unchanged, and the constant term \( -3 \) also stays as it is. Therefore, the simplified form is \( -4q^2 - q - 3 \). In summary: (a) \( 5x^2 + 7x \) (b) \( 7m^2 - m \) (c) \( -4q^2 - q - 3 \)