Why are you allowed to move the decimal points before dividing with decimals?

Mrs. sling bought a pound of green beans for $1.80. how much will mrs. tennison pay for 3 1/2 pounds of green beans?

Jack has a rectangular piece of land, the area of which is represented by a1 = 9.5l. his brother has a different rectangular piece of land, the area of which is represented by a2 = l(14 − l). let a represent the area in square meters and l represent the length in meters of the pieces of land. the two equations plotted on a graph meet at a point as shown in the image

Leo takes 30 minutes to eat dinner, 15 minutes to change clothes, and 20 minutes to walk to practice. if leo needs to be at hockey practice at 7: 15pm,.what time does he need to begin