First Part:
For every parenthesis with a plus sign to its left, you can eliminate the parenthesis (take into account that plus×minus=minus)
a + a - b - a + b
Then you add like terms. This means you add/subtract a with a and same with b and b (I'll organize the terms in alphabetical order but it's not neccesary)
a + a - a - b + b
Since a - a =0 and b - b = 0,
a + 0 + 0
Answer: a
Second part
Since you have a minus to the left of a parenthesis, you have to change the signs of all the terms inside the parenthesis before you eliminate the parenthesis.
Answer: 2a^2
For every parenthesis with a plus sign to its left, you can eliminate the parenthesis (take into account that plus×minus=minus)
a + a - b - a + b
Then you add like terms. This means you add/subtract a with a and same with b and b (I'll organize the terms in alphabetical order but it's not neccesary)
a + a - a - b + b
Since a - a =0 and b - b = 0,
a + 0 + 0
Answer: a
Second part
Since you have a minus to the left of a parenthesis, you have to change the signs of all the terms inside the parenthesis before you eliminate the parenthesis.
Answer: 2a^2