Wolfram Research
Wolfram Math World: Multiplicative Inverse
This site explains multiplicative inverse in nonzero real and complex numbers, as well as matrices. Also discusses how to detect the multiplicative inverse of complex numbers in a table.
Oswego City School District
Regents Exam Prep Center: Complex Fractions
Resources to help you plan classroom instruction on complex fractions: three lessons, with example problems and step-by-step solutions, on recognizing and simplifying complex fractions; a practice quiz through which students work on...
University of Cambridge
University of Cambridge: Nrich: Number Detective
On this one page website sharpen your logic and place value skills while working on this challenge. The solution is available to double check your solution.