The given polygons are similar
[tex]\sf{ \frac{2x}{42} = \frac{7}{y} = \frac{2z}{6} = \frac{21}{9} } \\ [/tex]
Answer
[tex]\sf{18. \: \frac{2x}{42} = \frac{21}{9}, \: \: 18x = 882 , \: \: x = 49 } \\ [/tex]
[tex]\sf{19. \: \frac{7}{y} = \frac{21}{9}, \: \: 21y = 63 , \: \: y = 3} \\ [/tex]
[tex]\sf{20. \: \frac{2z}{6} = \frac{21}{9}, \: \: 18z = 126, \: \: z = 7} \\ [/tex]
