1. 3a - 1 + 18 - a
So you can reorder these, as long as they keep the sign in front of them.
3a - a - 1 + 18, you can reorder it to.
And then just add or subtract.
2a + 17
2. (a+3) - (a + 2)
First you want to open the parenthesis.
To do that, check the symbol before the parenthesis.
If it's a minus, reverse the operator inside the parenthesis. If it's a plus, do nothing.
So just,
a + 3 - a - 2
Then reorder again
a - a + 3 - 2
1
3. 43 + a - 2a
Just subtract, a - 2a, to get -a.
So,
43 - a
