Which expression is equivalent to 36a-12b 4(6a-9b) 4(8a3b) 4(9a+3b) 4(9a-3b)

Amerchant has coffee worth $60 a pound that she wishes to mix with 50 pounds of coffee worth $90 a pound to get a mixture that she will sell for $70 a pound. how many pounds of the & 60 coffee should be used?

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

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.