a. \(\dfrac{5}{3}+\left(\dfrac{-2}{7}\right)-\left(-1.2\right)\)
= \(\dfrac{5}{3}-\dfrac{2}{7}+\dfrac{6}{5}\)
= \(\dfrac{175}{105}-\dfrac{30}{105}+\dfrac{126}{105}\)
= \(\dfrac{271}{105}\)
b.\(\dfrac{-4}{7}+\left(\dfrac{-5}{6}\right)-\dfrac{17}{4}\)
= \(\dfrac{-4}{9}-\dfrac{5}{6}-\dfrac{17}{4}\)
= \(\dfrac{-16}{36}-\dfrac{30}{36}-\dfrac{153}{36}\)
= \(\dfrac{-199}{36}\)