8. \( -15 m^{2} n^{4}-15 m^{2} n^{4} \) 10. \( 16 s+8 r-17 s \)

When combining like terms in the expression \( -15 m^{2} n^{4} - 15 m^{2} n^{4} \), you simply add the coefficients. This results in \( -30 m^{2} n^{4} \). It's all about keeping an eye on those coefficients and ensuring each term remains correctly grouped! For the expression \( 16 s + 8 r - 17 s \), you can group the \( s \) terms together. Here, \( 16 s - 17 s \) simplifies to \( -1 s \) or simply \( -s \). So you end up with \( -s + 8 r \). It's like cleaning up your room: clear the clutter by sorting out what belongs together!