Respuesta :

Triangle STU is similar to triangle SVW
so

  TU          ST
------- = ---------- (as you know SV = ST + TV  = 12 + 18 = 30)
  VW       SV
so
  TU          12
------- = ---------- 
  40          30

TU = 12 * 40 / 30
TU = 16

answer
16 inches
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