That just means you need to find the factors of both numbers.
The factors for 81 are: 1, 3, 9, 27, and 81
The factors for 100 are: 1, 2, 4, 5, 10, 20, 25, 50, and 100.
You can check to see if these work by multiplying the numbers. So for 81, you would multiply 1 * 81, 3 * 27, and 9 * 9, which all equal 81. And for 100, you would multiply 1 * 100, 2 * 50, 4 * 25, 5 * 20, and 10 * 10, which all equal 100.
