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 + 21) both lie on the line defined by the equation x = (y/7) - (2/5), what is the value of p?	Select the correct option.
A) 1 B) 2 C) 3 D) 4 E) 5

Rationale: x = ( y / 7 ) - ( 2 / 5 ) , and so y = 7 x + 14 / 5 . the slope is 7 . ( n + 21 - n ) / ( m + p - m ) = 7 p = 3 the answer is c .
Answer: C