a. 0,5.\(\sqrt{100}\)-\(\sqrt{\dfrac{1}{49}}\)+\(\sqrt{225}\)
b. 6.\(\left(-\dfrac{2}{3}\right)+12.\left(-\dfrac{2}{3}\right)^2+18\left(-\dfrac{2}{3}\right)^3\)
c. \(\left(2,5+3,75-\dfrac{5}{8}+\dfrac{10}{15}\right)\): \(\left(8,5+12,75-\dfrac{17}{8}+\dfrac{34}{15}\right)\)