Answer: Yes they could.
Step-by-step explanation:
The two pairs of sides given are proportional: 3/7 : 9/21
The two triangles have the side:side ratio, meaning they are similar
Because they are similar, their hypotenuses <em>could</em> lie along the same line, not guaranteed, but possible.
Step-by-step explanation:
that's for Part B
Part C: triangles PQR and P"Q"R" are not congruent since the corresponding sides are not equal