Respuesta :

sherry318
First set up a proportion because they are similar triangles:
9/3x-20 = (72+9)/(56+3x-20)
9/3x-20 = 81/3x+36
9(3x+36) = 81(3x-20)
27x+324 = 243x-1620
1944 = 216x
x = 9

Answer:

Step-by-step explanation:

9 cm/72 cm=3x-20/56

3x-20=56/8. (9÷72=1/8)

3x-20=7

3x=7+20

3x=27

x=27/3

x=9

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