The +51 is regardless (being the y intercept) so it does not affect our answer. If the employee has to drive one mile (x=1) it will take 7.76 + 51 min to get there. If they have to drive 0 miles (x=0) it will only take 51 min. This is a difference of 7.76. You really just need to take the slope (I just used this example to make it make more sense) as x is the number of miles the employee has to drive, and therefore that times 7.76 would be how much longer it would take to drive to work.
