When dividing variables with exponents, subtract the bottom exponent from the top. since there is no "a" in the denominator, we would leave it as is. The "b" at the top (numerator) has an exponent of 4, and the one in the bottom (denominator) has an exponent of 2, so we would do 4 - 2, which equals 2, so the exponent on b would be 2. Then, the exponent for 5 in the numerator is 4, and in the denominator, it's 1 (any number that with no visible exponent has an exponent of 1). 4 - 1 is 3, and 5^3 is 125.