Given: Equation of planes is: 2x−y+3z+4=0 and 6x−3y+9z−3=0 The given equations can be re-written as: 2x−y+3z+4=0 and 2x−y+3z−1=0 As we can see that, both the planes are parallel to each other and the distance between two parallel planes is given by: a2+b2+c2d1−d2 Here, a=2,b=−1,c=3,d1=4 and d2=−1⇒22+(−1)2+324+1=145