If triangles ADE and ABC shown in the
figure to the right are similar, what is the
value of x?
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Step-by-step explanation:
similar means that (with all angles being the same) the side lengths of one triangle all correlate to the corresponding side lengths of the second triangle by the same factor.
and so, because AD = 2 is 1/3 of AB = 4+2 = 6, we need to apply the same factor 1/3 to x compared to 12.
12 × 1/3 = 4.
so, A is correct.