Jennie was using the properties of operations to help her use mental math to subtract the rational numbers shown. Look at Jennie's strategy. What property of operations did Jennie use in Step 3?

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z

Ateacher wanted to buy a chair, a bookshelf, two tables and a desk. she spent $900 for all five items and the chair and the desk combined 70% of her total. if the bookshelf cost $50, how much did each of the tables cost?