Answer :

[tex]72-x+20=70 \\ \\ 92-x=70 \\ \\ -x=-22 \\ \\ x=22 \\ \\ blank=22[/tex]
[tex]72-x+20=70 \\ -x+92=70 \\ -x+92-92=70-92[/tex]

Divide both sides by -1

[tex] \frac{-x}{-1} = \frac{-22}{-1} =22[/tex]