The New River Gorge bridge in West Virginia is a steel arch bridge 518m in length. How much does the total length of the roadway decking change between temperature extremes of -20.0C and 35.0 C? The result indicates the size of the expansion joints that must be built into the structure.

average linear expansion coefficient for steel: 11x10^-6

deltaL=L*deltaT*coeffcient

Delta Temp here is 55C, you are given L, and the coefficent. I assume the coefficent is in Celcius, not F.

yeah. sorry.
i got the answer.