Hi again! So to explain this one, we need to prove that two of the triangles sides are in the same ratio and we need to prove that one angle is congruent between the two triangles (Side-Angle-Side Postulate of Similarity). If the ratios are not equal, then the triangles are not similar. To start, notice that RN is similar to side RP and RM is similar to side RQ. RN:RP (ratio) = 6:12 = 1:2. But, realize that RM:RQ = 8:18 = 4:9. This is not equal to 1:2. Thus, though the triangles have one angle in common, they are not similar.