Simplify 2ab+4ac-5c+-6c+7ab

Replace all occurrences of ${\displaystyle +}$${\displaystyle -}$ with a single ${\displaystyle -}$. A plus sign followed by a minus sign has the same mathematical meaning as a single minus sign because ${\displaystyle 1\cdot -1=-1}$

Add ${\displaystyle 2ab}$ and ${\displaystyle 7ab}$.

Subtract ${\displaystyle 6c}$ from ${\displaystyle -5c}$.