Answer: A. 12
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Work Shown:
LK = 65
LR = 52
RK = LK - LR = 65 - 52 = 13
The triangles are similar, so the corresponding sides form equal ratios
LK corresponds to RK as they are both on the same side
LK/RK is one ratio and it is equal to MK/SK
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LK/RK = MK/SK
65/13 = 60/x
65x = 13*60 ... cross multiply
65x = 780
x = 780/65 ... divide both sides by 65
x = 12
SK = 12