Answer:
║JF║=75
Step-by-step explanation:
angle JDF = angle JYS ( corresponding angles)
angle JYD = angle JSF ( corresponding angles)
JD/JF=JY/JS=DY/FS
Use JD/JF=JY/JS and substitute:
50/x=42/63, where║JF║
cross multiply
50×63=42×X
3150=42x
divide via by 42
3150/42=42x/42
75=x
x=75
So ║JF║=75
Hope this helps.
