we can say the triangles in Q.7 are congruent as they follow the axiom A.S.S.
Since in there is (i) right angle in both triangle
(ii) there is a common sides between the triangles
(iii) one of the sides are equal in both triangles
But in Q.8, there is only two information and they are
(i)there is a equal sides in both triangles
(ii) two angles are equal due to the property of vertically opposite angles.
the third information is missing and we need at least three information.
Hence we cant say the triangles are congruent without full information.