20x + 50 (option B)
Explanation:[tex]5(3x\text{ + 10) + 5x}[/tex]Expanding the parenthesis:
[tex]5(3x)\text{ + 5(10) + 5x}[/tex][tex]\begin{gathered} \text{simplifying:} \\ 15x\text{ + 50 + 5x} \end{gathered}[/tex]collecting like terms:
[tex]\begin{gathered} 15x\text{ + 5x + 50} \\ 20x\text{ + 50 (option B)} \end{gathered}[/tex]