Question

12 miles is approximately equal to 6 km. How many km are equal to 18 miles? How many miles are equal to 42 km? 

Answer 1

if 
12 miles =19.3121 km
18 miles=28.9682km
42 km=26.0976miles

Answer 2

if 12 miles=6km
then 18 miles =6/12 x 18
                       =1/2 x18
                       =9 km
 
 then 42km=12/6 x 42
                   =2 x 42
                    =84 miles