Question

Anna has $45 to spend on felt to make banners for an upcoming game. Gold felt costs $5 per yard and blue felt costs $4 per yard. Anna needs at least 7 yards of felt to make the banners. Which is a solution for this situation?

Answer 1

For this case you must make a system of equations that suits the situation you want to solve.
 We have then:
 x: Gold felt
 y: Blue felt
 Writing the system of equations:
 x + y> = 7
 5x + 4y = <45
 Solving the system of equations:
 Step 1: Multiply equation 1 by -4
 -4x -4y = -28
 5x + 4y = 45
 Step 2: add equations:
 x = 45-28
 x = 17
 Clearing y:
 y = 7-x = 7-17 = -10
 y = -10
 answer
 You can buy between 7 and 9 Gold felt