How can the explicit formula of an arithmetic sequence be rewritten as a linear function?

If x = 12 and y = 3, what is the value of x - y 2? 81 6 3 18

Of four points are collinear, they are also coplanar

Afamily has five members. a mom, a dad, two sisters, & a brother. the family lines up single file. what is the probabillity that the mom is at the front of the line