The line ax + by + c = 0 can be written as y = mx + c, where m is the slope of the line and c is the y-intercept.

6x + 3y - 15 = 0

=> 3y = -6x + 15

=> y = -2x + 5

**Therefore the slope is -2.**

The line ax + by + c = 0 can be written as y = mx + c, where m is the slope of the line and c is the y-intercept.

6x + 3y - 15 = 0

=> 3y = -6x + 15

=> y = -2x + 5

**Therefore the slope is -2.**