1. The problem is to find the total number of pages in Liam's and Mason's books combined. 2. Liam's book pages are given by the expression $2x + 10$. 3. Mason's book pages are given by the expression $3x + 5$. 4. To find the total pages, we add the two expressions: $$ (2x + 10) + (3x + 5) $$ 5. Combine like terms: $$ 2x + 3x + 10 + 5 = 5x + 15 $$ 6. So, the total number of pages is $5x + 15$. 7. From the options given, $8x + 15$ is close but the coefficient of $x$ is incorrect. 8. The correct total pages expression is $5x + 15$, which matches none of the options exactly. 9. Therefore, the total pages expression is $5x + 15$.