Selena spends $53.94 to buy a necklace and a bracelet set for each of her friends. Each necklace cost 9.99, and each bracelet costs 7.99. How many necklace and bracelet sets, s, did selena buy?

She bought 3 necklace and bracelet sets

If i can be brainliest that would be great

Step-by-step explanation:

Each set contains a necklace and a bracelet

∵ Each necklace cost $9.99

∵ Each bracelet cost $7.99

∴ The cost of one set = (9.99 + 7.99)

∵ She spent on them $53.94

- Add the cost of a necklace and the cost of a bracelet and

 multiply the sum by x  and then equate the product by 53.94

∴ (9.99 + 7.99)x = 53.94

∴ 17.98 x = 53.94

- Divide both sides by 17.98

∴ x = 3

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.