Respuesta :

Answer:

BC = 20

Step-by-step explanation:

This is an isoceles triangle so AB = CB

If AB = CB then 3x = 5x - 20

3x - 5x=  - 20

-2x = -20

x = -20/-2

x = 10

BUT length BC is 5x - 20

so 5(10) - 20

50 - 20

BC = 30

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