On a buying trip in Los Angles, Rihanna ordered 120 pieces of jewelry; a number of bracelets at $7 each and a number of sets of earrings at $13 each

Question

math question about elimination method/multiplying whichever method 

 

On a buying trip in Los Angles, Rihanna ordered 120 pieces of jewelry; a number of bracelets at $7 each and a number of sets of earrings at $13 each. She wrote a check for $1020 to pay for the order. How many bracelets and how many sets of earrings did Rihanna purchase?

 

 

Answer 1

If the question is considering the set as on piece of jewelry, we have x: bracelets y: earrings

 

So equation 1: x + y = 120

    equation 2: 7x + 13y = 1020

  

Multiply equation 1 by -7

  so              -7x -7y = -840

 

added to equation 2

                  7x + 13y = 1020

gives us          6y = 180

divide by 6        y = 30. 

this means you have 30 earrings and to find x plug 30 in for y and solve the equation for x.