The distance is 2.23606 (2.24 rounded)
Two lines to be parallel their slopes have to be equal.
so m1 = m = 4
y = mx + b ( Slope intercept form)
y = 4x + b
(3,0) is on the line:
0 = 12 + b
b = -12
y = 4x - 12
X - the number
The algebraic expression:

The solution: