Question

Seven x's and 3y's cost as much as 4z's. One z costs as much as 1x plus 1y together. How many x's cost as much as 1y?

Answer 1

Answer:

Step-by-step explanation:

Equations

7x + 3y = 4z

Second equation

x + y = z                          Multiply the entire equation by 4

4[x + y = z]                      Now distribute the 4 through the equation

4x + 4y = 4z                    Both equations = 4z. Equate the lefts.

Third equation  

7x+3y = 4x + 4y              Subtract 3y from both sides

7x + 3y -3y = 4x + 4y -3y

7x = y + 4x                      Subtract 4x from both sides

7x - 4x = y + 4x - 4x       Combine

3x = y

Answer: 3x = y