Abottle contains 20fluid ounces of lotion and sells for $5.80.the 20-fluid -ounce bottle contains 125% of the lotion in the next smallest size, which sells for $5.12.which is the better buy.explain.

If the 20 fl.oz bottle contains 125% of the next smallest size, the next smallest bottle should be 4/5 of the 20fl. oz bottle.
That means the smaller bottle has 16 fl. oz (you can check it, multiply 16 by 1.25 and you get 20).
Next, you can find the price as dollars per fluid ounce.
The bigger bottle will be: 5.8/20=$0.29
The smaller bottle: 5.12/16=$0.32
In this case, the larger bottle is the better buy because you pay less per fluid ounce of lotion.

When the first equation is multiplied by -3, the sum of the two equation and any of the original equations will have the same solution as the original equations. Hence 5x = -10 and 11x - 9x = -13 will have a solution of (-2, -1).