Three different members of the set {4,5,6,7,8,9} are chosen at random and added. how many different sums are possible?

The area of a rectangle is 54x^9y^8 square yards.if the length of the rectangle is 6x^3y^4 yards,which expression represents the width of the rectangle in yards

Agroup of students want to create a garden. they do not know the exact measurements but they propose using a variable to represent the length and width of the garden. the length of the garden is 10 feet longer than double the width. use a single variable to write algebraic expressions for both the length and width of the garden. write an algebraic expression for the area of the garden. use mathematical terms to describe this expression.

How do i start to solve? would appreciate a walk-thru! a bird sitting 16ft above the ground in an apple tree dislodges an apple. after how many seconds does the apple land on the ground? (assuming that no branches will interfere with it's fall)