In simple steos how do you find the greates common factor

1. You choose 2 or more numbers (lets say 8 and 42)
2. You find ALL of the factors of the two numbers(8:1,2,4,8; 42: 1, 2, 3, 6, 7, 14, 21, 42)
3. You find equivalent, or the same factors of both numbers (8,12:1, 2)
4. The you se the last number on the common factors. he last number (which is 2) is the GCF

Hope this helps

4x 20 is 80 but if ther machine is broken then there is none you have to redo the test