\displaystyle  \text{v) }\Big(6   \frac{4}{11}   \Big)^2-\Big(4   \frac{7}{11}   \Big)^2 = \Big(6   \frac{4}{11}   +4   \frac{7}{11}   \Big) \Big(6   \frac{4}{11}   -4  \frac{7}{11}   \Big) = 11 \times 1   \frac{4}{11}   = 19 