Question

how will you add to subtract from and intersect new selection with old selection​

Answer 1

Select a selection tool, and do one of the following: Hold down Shift (a plus sign appears next to the pointer) to add to the selection, or hold down Alt (Option in Mac OS) to subtract (a minus sign appears next to the pointer) from a selection. Then select the area to add or subtract and make another selection.

Answer 2

Answer:

Select the Quick Selection tool . (If the tool isn't visible, hold down the Magic Wand tool .) In the options bar, click one of the selection options: New, Add To, or Subtract From.

Explanation:

Hope its helpful.