Are these triangles similar?
Nope. They are not similar. Only UT and XW are proportional, while the others are not. You know this by 12 times 2 = 24, which is XW to UT.
ΔSTU ~ ΔVWX ⁶/₁₂ = ¹²/₂₄ ¹/₂ = ¹/₂These triangles are similar.