SAS, twice
SAS congruence: two sides and the included angle equal the matching two sides and included angle. Scale factor 1. Figures congruent, hence also similar.
SAS similarity: one pair of congruent included angles, and the two sides that make those angles proportional. Scale factor can be anything. Figures similar, congruent only if that factor is 1.
The sides have to be the ones that create the marked angle. If the labeled lengths are not those two sides, you cannot name SAS similarity even if an angle matches.
SSS, twice
SSS congruence: three pairs of equal sides. SSS similarity: three pairs of proportional sides, one k for all three.
Keep one triangle in the numerators. Mixing 8/2 with 3/12 is a flipped pair and will fail the check even when the triangles are similar.
If you have no angle marks, SSS similarity is the route. If you have two angle marks, AA is faster.
Nested triangles
A small triangle sharing angle A with a big one, ΔABC ~ ΔADE. Then AD/AB = AE/AC. If AD = 8, AB = 14, AE = 4, then 8/14 = 4/AC, so AC = 7.
Do not pair the leftover outer segment with a whole side. The similarity statement tells you which lengths belong together.