Arailroad crew can lay 7 miles of track each day. they need to lay 203 miles of track. the length, l (in miles), that is left to lay after d days is given by the
following function.
i(d) = 203-7d

in geometry, parallel lines are lines in a plane which do not meet; that is, two lines in a plane that do not intersect or touch each other at any point are said to be parallel. by extension, a line and a plane, or two planes, in three-dimensional euclidean space that do not share a point are said to be parallel.