with the pythagorean theorem

using the formula of the quadratic equation

the length cannot be negative, therefore x=7
length of the shorter leg is: 7ft
length of the longer leg is: 3+3(7)= 24ft
length of the hypotenuse is: 4+3(7)= 25ft
The train is traveling at 165 mph
495/3=165
825/5=165
1155/7=165
1485/9=165