What should be subtracted from 12a – 16b to obtain -a – b?
13a – 15b
Here we have to identify the difference and take that away from the other expression.
The difference is –a –b.
(12a – 16b) – (-a – b) = 12a – 16b + a + b
= 12a +a -16b + b
= 13a – 15b