Cho tập số tự nhiên từ 1 đến 20, lấy ngẫu nhiên ba số. Xác suất để ba số lấy được lập thành cấp số cộng là

Need on this one asap im almost done with this subject

Spencer has 1/3 pound of nuts he divides them equally into 4 bags what fraction of a pound of nuts is in each bag

A)a square brown tarp has a square green patch green in the corner the side length of the tarp is (x + 8) and the side length of the patch is x what is the area of the brown part of the tarpb)a square red placemat has a gold square in the corner the side length of the gold square is (x - 2) inches with the width of the red region is 4 in what is the area of the red part of the placemat