Question

The figures are similar. find x. 9/21 6/x. X=?

Answer 1

since the figures are similar, then we can just use proportions on the corresponding sides.

$\bf \cfrac{\textit{large figure}}{\textit{small figure}}\qquad \qquad \cfrac{x}{6}=\cfrac{21}{9}\implies \cfrac{x}{6}=\cfrac{7}{3}\implies 3x=42 \\\\\\ x=\cfrac{42}{3}\implies x=14$