Write the measures of its sides in ascending order in each of the following triangles:
$(1)$ In $\Delta ABC$,$\angle B = 70^{\circ}$ and $\angle C = 20^{\circ}$.

(N/A) In $\Delta ABC$,the sum of angles is $180^{\circ}$.
Therefore,$\angle A + \angle B + \angle C = 180^{\circ}$.
$\angle A + 70^{\circ} + 20^{\circ} = 180^{\circ}$.
$\angle A + 90^{\circ} = 180^{\circ}$,so $\angle A = 90^{\circ}$.
The angles are $\angle C = 20^{\circ}$,$\angle B = 70^{\circ}$,and $\angle A = 90^{\circ}$.
Since the side opposite to the smaller angle is smaller,the order of sides is $AB < AC < BC$.