What does your instructor/textbook/worksheet mean by "rearrange this equation?" For instance, my interpretation suggests that if the original equation was:
3 + x = 7 + y
Then, the following would be four possible "rearrangements:"
x + 3 = 7 + y
3 + x = y + 7
x - 4 = y
x = y + 4
Is the above perhaps something similar to what you're expected to do? The more specific you can be about what the problem is asking, the better our help will be.