Answer:
7ab - 5a
Explanation:
For addition and subtraction this type of variable we should always keep one thing in mind that, we can only add or subtract only those digits whose variables are the same.
Solving given equation step to step:
(2ab - 5a - 7) - (-5ab - 7)
Opening the bracket first,
⇒ 2ab - 5a - 7 - (- 5ab) - (- 7)
⇒ 2ab - 5a - 7 + 5ab + 7
Now, taking same variables digits together
⇒ (2 + 5)ab - 5a - 7 + 7
⇒ 7ab - 5a - 0
⇒ 7ab - 5a