\( \begin{array}{ll}\text { a) } 8 x+5 x & \text { б) } x+21 \cdot x+10 \quad x\end{array} \)

First, let's add the terms in the first expression: \(8x + 5x\) simplifies to \(13x\). You combine the coefficients (8 and 5) because they are like terms. For the second expression, we distribute the terms: \(x + 21 \cdot x + 10x\) simplifies to \(x + 21x + 10x = 32x\). Here, we distribute \(x\) in front of \(21x\) and \(10x\), ultimately leading to a total of \(32x\).