Convert the negative exponents to positive exponents inside the parentheses. Recall that a factor can be moved from the denominator to the numerator or from the numerator to the denominator of a fraction if the sign of its exponent is changed. So$,$ a$2$ in the denominator can be written as a$2$ if moved to the numerator. Similarly, b$4$ in the denominator can be written as b$4$ if moved to the numerator. $15$a$3$b$212$a$2$b$44=124$