Letter b on number 11 is all I need help with. Thank you

distance = 500 feet
Since Δ VWX and Δ YZX are similar then the ratios of corresponding sides are equal, that is
[tex]\frac{VW}{YZ}[/tex] = [tex]\frac{VX}{YX}[/tex] = [tex]\frac{WX}{ZX}[/tex]
completing the required values gives
[tex]\frac{100}{l}[/tex] = [tex]\frac{60}{30}[/tex] ( cross- multiply )
60l = 30 × 100 = 3000 ( divide both sides by 60 )
l = 500
distance across the swamp is 500 feet