Mcqueen: 4/10 of 10 km
Multiply 4/10 by 10 :
4/10 x 10 = 4 km
Mate = 0.5 of 10 km
0.5 x 10 = 5 km
Selly: 15/20 of 10 km
15/20 x 10 = 7.5 km
So, we have:
Mc queen: 4 km
Mate: 5 km
Selly: 7.5 km
By looking at the number line:
1-Selly goes first
2-Mcqueen goes last
3-Selly is located in the arrow (7.5km)