The number 6 is halfway between 2.8
the number 6 is halfway between -12

If 6 is halfway between 2.8 and x, then the distance from 2.8 to 6 is 1/2 the distance from 2.8 to something
find the distance

6-2.8=3.2
1/2 distance=3.2
multiply by 2 to find whole distance
3.2 times 2=6.4
add
2.8+whole distance=2.8+6.4=9.2

6 is halfway between 2.8 and 9.2

6 is halfwa between -12 and something
find distance
6-(-12)=6+12=18
1/2 distance=18
times 2
18*2=36
add
-12+36=24

6 is halfway between -12 and 24

blanks are
6 is halfway betwen 2.8 and 9.2
6 is halfway betwen -12 and 24