a×b=a+b=2ab.
Assuming a×b=ab means the product of a and b, and a+b means the sum of a and b, then ab=2ab, so 2ab-ab=ab=0, and at least one of a or b is zero.
If a=0, a+b=b, and therefore b=ab=0, so b=0.
If b=0, a+b=a, and therefore a=ab=0, so a=0.
The conclusion is that there is one solution: a=b=0.
2×(2×3)+5=17 seems to have nothing to do with the first part of the question.