13) (3¹/₃)²

$$3\frac{1}{3} = \frac{3 \cdot 3 + 1}{3} = \frac{10}{3}$$

$$\left(\frac{10}{3}\right)^2 = \frac{10^2}{3^2} = \frac{10 \cdot 10}{3 \cdot 3} = \frac{100}{9} = 11\frac{1}{9}$$

Ответ: 11¹/₉