ข้อสอบคณิต O-NET - 2561

$$\begin{gathered} \mathrm{จากโจทย์} \\ \mathrm{จะได้} A = \left\{1, 2, a, b, d\right\} - \left\{1, b, c\right\} \\ = \left\{2, a, d\right\} \end{gathered}$$

$$\begin{gathered} B = \left\{2, 3, c\right\} \cup \left\{2, b, d\right\} \\ = \left\{2, 3, b, c, d\right\} \\ C = \left\{1, 2, 3, b\right\} \cap \left\{3, a, b\right\} \\ = \left\{3, b\right\} \end{gathered}$$

$$\begin{gathered} \mathrm{ดังนั้น} B\cap \left(A\cup C\right) = \\ \left\{2, 3, b, c, d\right\} \cap \left(\left\{2, a, d\right\}\cup \left\{3, b\right\}\right) \\ \left\{2, 3, b, c, d\right\} \cap \left\{2, 3, a, b, d\right\} \\ \left\{2, 3, b, d\right\} \\ \mathrm{มี} 4 \mathrm{จำนวน} \end{gathered}$$