Take a rectangular piece of paper. Fold the opposite ends, so that the folding lines are parallel. How do you know they are parallel?

If you roll two fair dice (one black die and one white die), in how many ways can you obtain a 4 on at least one die?

If an athlete can bike 6 miles in 25 minutes, how many miles will he bike in an hour and half if he continues to bike at the same rate?

Kelly is a salesperson at a shoe store, where she must sell a pre-set number of pairs of shoes each month. at the end of each work day the number of pairs of shoes that she has left to sell that month is given by the equation s=300-15x , where s is the number of pair of shoes kelly still needs to sell and x is the number of days she has worked that month. what is the meaning of the number 300 in this equation