Answer: 130 stamps.
Step-by-step explanation:
Let amount оf the stamps Debbie must give to Mark so that Mark have 120 more than she is x.
Hence,
(580+x)-(720-x)=120
580+x-720+x=120
2x-140=120
2x=260
2*x=2*130
x=130.
So, 130 stamps Debbie must give to Mark so that Mark have 120 more than she.
Good luck an' have a nice day!
