Answer:
BC = 28
Explanation:
Since the triangles are similar then the ratios of corresponding sides are in proportion, that is
= ( substitute values )
= = 4 ( multiply both sides by 7 to clear the fraction )
BC = 4 × 7 = 28
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= 
( substitute values )
= 
= 4 ( multiply both sides by 7 to clear the fraction )