m and n are the x and y coordinates, respectively, of a point in the coordinate plane. If the points (m, n) and (m + p, n + 9) both lie on the line defined by the equation x = (y/3) - (2/5), what is the value of p? Choose the correct option.
A) 1
B) 2
C) 3
D) 4
E) 5

Rationale: "x = ( y / 3 ) - ( 2 / 5 ) , and so y = 3 x + 6 / 5 . the slope is 3 . ( n + 9 - n ) / ( m + p - m ) = 3 p = 3 the answer is c ."
Answer: C