Sara has six necklaces, but her mother will only allow her to wear two at a time. How many different combinations of two necklaces can Sara wear?

15
12
360
30

The length of a rectangle plus its width is 25 cm. the area is 156 square cm. what are the length and width of the rectangle? separate the answers with a comma.

David is spreading mulch on a triangular area of his flower bed. the coordinates of the vertices of the area are (1, 3), (9, 3), and (4, 6). what is the area of the triangle if each square has an area of 3 square feet?

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers