9(30+7) = (9*30)+(9*7)
This is the distributive property
x(y+z) = xy + xz
Let the dash = x
9(30+7) = (9*x)+(9*7)
9(37) = 9x + 63
333 = 9x + 63
Substract 63 from both sides
333 - 63 = 9x +63-63
270 = 9x
Divide both sides by 9
270/9 = 9x/9
30 = x
Or x = 30