Math 30 points

add and subtract and show all work for each problem by grouping to identify the like terms before you simplify

a. (-2x^2 -4x+13) + (12x^2 +2x-25)

b. (7x^2 +4x-26) - (-7x^2 -3x+15)

if possible explain why you did each step because i am having trouble with problems like these but you dont have to, just show work.