What's the difference between -1/2 and 1/6

Acircle has a circumference of 28.36 units what is the diameter of the circle

60 2(x + 2) in the diagram, gef and hef are congruent. what is the value of x?

When you have 25 numbers, and jake picks 3 random numbers and puts them back, what is the chance bob has of picking those 3 numbers when he picks 6 random numbers (without putting them back)? explain.