E&M Physics Problem?

Question

It goes point A to R1 to +- battery (V1) to R2 to -+ battery(V2) to point B. The current flows from A to B.

If a current I=5 A exists between points a and b, R1=7 Ω, R2=8 Ω, V1=16 V, and V2=3 V,the voltage difference Va−Vb is

Answer 1

Zero.
From your description, there is nothing which may drop voltage between A and B.