To convert a decimal into a fraction, we need to determine the place value of each digit in the decimal. In this case, the decimal .125 has three digits after the decimal point, which means it is in the thousandths place. To convert it into a fraction, we can write it as 125/1000. Then, we simplify the fraction by dividing both the numerator and denominator by their greatest common divisor, which is 125. By dividing both numerator and denominator by 125, we get 1/8. Therefore, the decimal .125 is equal to the fraction 1/8.