Question

72 - (blank) + 20 = 70 what number is the blank

Answer 1

$72-x+20=70 \\ \\ 92-x=70 \\ \\ -x=-22 \\ \\ x=22 \\ \\ blank=22$

Answer 2

$72-x+20=70 \\ -x+92=70 \\ -x+92-92=70-92$

Divide both sides by -1

$\frac{-x}{-1} = \frac{-22}{-1} =22$