If the numbers in the bottom row are a, b, c, and d, the numbers in the second row must be a+b, b+c, and c+d.

The third row numbers would be a+2b+c and b+2c+d.

The top block would contain a+3b+3c+d.

But the second row numbers are given to be equal, therefore a+b=b+c, so a = c; also b+c=c+d so b=d.

Substitute into the top block expression to get a+3b+3c+ b or 4b+4c, which must be a multiple of 4.