To simplify the expression B/(a^2 - ab) + a/(b^2 - ab), we can first factor out the common term "ab" from the denominators:

B/(a(a - b)) + a/(b(b - a))

Next, we need to find a common denominator for the two fractions. In this case, the denominators are a(a - b) and b(b - a). To find a common denominator, we can multiply the two denominators together:

a(a - b) * b(b - a)

Next, we rewrite the fractions with the common denominator:

Bb/(a(a - b) b(b - a)) + a(a - b)/(b(a - b) b(b - a))

Now, we can combine the fractions:

(Bb + a(a - b))/(a(a - b) * b(b - a))

Finally, we can simplify the expression by expanding Bb + a(a - b) in the numerator:

(Bb + a^2 - ab)/(a(a - b) * b(b - a))

Therefore, the simplified expression is:

(Bb + a^2 - ab)/(ab(a - b)(b - a))