a)  ${1,2}^3\cdot 5^3={\left(1,2\cdot 5\right)}^3=6^3=216$  

b)  ${2,5}^{13}\cdot {\left(-\frac{2}{5}\right)}^{13}={\left(2,5\cdot \left(-\frac{2}{5}\right)\right)}^{13}={\left(\frac{5}{2}\cdot \left(-\frac{2}{5}\right)\right)}^{13}={\left(-1\right)}^{13}=-1$