Step-by-step explanation:
Diego has run  2/3 of a race's
Let total distance of the race = y
He has run 8 & 1/2 kilometers.
This means 2/3 of y = 8 & 1/2 km
How long is the whole race?
2 / 3  x  y  = 8 & 1/2
The following equations can be used to calculate the distance of the whole race;
8 & 1/2 divided by 2/3 = ?
2/3 x ? = 8 & 1/2
8 & 1/2 times 3/2 = ?