Answer:
x = 6
Explanation:
To find the missing side, write a proportion using side lengths from each similar shape. A proportion is an equation that sets equal two ratios.
![(4)/(12)=(x)/(18)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/53bxvwiplgu1zon0c94g8e6ntetzsu1ynq.png)
Find x by cross multiplying numerator and denominator of each fraction.
4(18) = 12x
72 = 12x
6 = x