What is the gcf of 16s3t, 40s5, and 68t2?

The greatest common factor is the largest number that is a factor of all 3 numbers.

16s^3t, 40s^5, and 68t^2

In this case, we don't even need to worry about the variables because they do not occur in all 3 numbers.

Let's worry about the coefficients:

16, 40, and 68

Let's try to divide each number by 4.

16 / 4 = 4

40 / 4 = 10

68 / 4 = 17

Since 17 is prime, 4 is the largest factor of each number. Therefore, the GCF of the three expressions above is 4.

No a triangle cannot be formed because when you add the two smallest number together (which would be 11) the have to be bigger than the number it is "against" ( which would be 12)