i don't understand how to simplify this
6A-7B+11-9A+6B-15
group common factors...
(6A-9A)+ (6B-7B) + (11-15)
now add/subtract within those alike factors.
6A-7B+11-9A+6B-15
(6A-9A)+ (6B-7B) + (11-15)
now add/subtract within those alike factors.