Answer: the page numbers are 253 & 254
Explanation:
Let the lower page number be x.
The the higher page number is x+1
Added together, they are 507, so ...
x + (x + 1) = 507
2x + 1 = 507
2x = 506
x = 253
x+1 = 254
Check answer: 250+3 + 250+4 = 250+250 + 3+4 = 500 +7 = 507 - -Checks!
Hope this helps!