Find the greatest common divisor of 164 and 100. Use that number to reduce both the numerator and denominator. You can start with 2 since both are even numbers. If you you still have even numbers in both the numerator and denominator after dividing by 2, then the greatest common divisor of 164/100 is a number that's larger than 2. You get 84/50, which also has at least one common divisor, when you divide 164/100 by 2. The goal is to reduce 164/100 to a fraction whose numerator and denominator have no common divisor other than 1.
You could also take a shortcut to find the greatest common divisor. To find one for 164, think of a number that divides evenly into 16. Then you're left with 4. What number divides evenly into 4? Does that same number divide evenly into 100? Hope that helps.
