Greatest common factor of 50,40,and 20

Which one ? is the answer and how to find this answer

If x = -2, then x 2-7x+10 equals a. 0 b.20 c.28

Boris needs to buy plastic spoons. brand a has a box 42 spoons for $2.37. brand b has a box of 72 spoons for $3.57. find the unit price for each brand. then state which brand is the better buy based on the unit price. round your answer to the nearest cent.