if the line containing the points (a,3) and (b,2) has a slope of 1/7, then a-b=

Slope :

m = ( y2 - y1 ) / ( x2 - x1 )

In this case :

x1 = a

x2 = b

y1 = 3

y2 = 2

m = ( y2 - y1 ) / ( x2 - x1 ) = 1 / 7

( 2 - 3 ) / ( b - a ) = 1 / 7

- 1 / ( b - a ) = 1 / 7

Reciprocal value :

- ( b - a ) = 7

- b + a = 7

a - b = 7