#### Answer

-1/30

#### Work Step by Step

In order to do this problem, recall (1) that addition and subtraction come after multiplication and division in order of operations, (2) that when there is a tie in order of operations, it is done from left to right, and (3) that dividing by a fraction is the same as multiplying by that fraction's reciprocal.
$$= \frac{4}{5} - \frac{10}{12} - \frac{5}{6} \times \frac{14}{8} + \frac{10}{21} \\ = \frac{4}{5} - \frac{10}{12} - \frac{70}{48} + \frac{10}{21}$$
Using common denominators, we obtain:
$$1/30$$