-77 PEMDAS is the process you would use and you would have to do the associative property with-(3--4)
The race is 111.6 m long.
8 hurdles spaced 12.3 m apart means 7 spaces that are 12.3 m in length; 7*12.3 = 86.1
Add to this the distance to the first hurdle and the distance from the last hurdle:
86.1+15+10.5 = 111.6 m