Answer: 3 Sets of the 4 post cards and 3 of the single post cart sets.
Step-by-step explanation:
You buy 3 of the 4 post card set becuase that is the most you can get of those to get under 15 post cards.
You would now have 12 postcards now you have to buy 3 of the single set to get to 15 cards
X=13 i believe!! hope it helps <3
Answer:

Step-by-step explanation:
bx-c=ax+d
<=> bx-ax=c+d
<=> (b-a)x=c+d
<=> x=(c+d)/(b-a)
You want to divide the cost of the books by the total costs.
308/2800 = 0.11
You then need to convert 0.11 to a percent: 0.11 = 11%
Therefore, 11% of her costs last semester were spent on books.
That’s too much!
Answer:
Our system of equations is:
We are looking for x
Let's express y using x
Replace x in the second equation with the result
- 4y-4x²-12x = -7
- 4(-2x-1)-4x²-12x = -7
- -8x-4-4x²-12x = -7
- -8x-4x²-12x = -7+4
- -4x²-20x = -3
- -4x²-20x+3 = 0 multiply by -1 to get rid of the - signs with x
- 4x²+20x-3=0
4x²+20x+3=0 is a quadratic equation
Let Δ be our discriminant
Δ= 20²-4*4*(-3)
Δ=448 > 0 so we have two solutions for x
let x and x' be the solutions
- x =
= -5.145 ≈ -5.15 - x'=
= 0.145≈ 0.15
so the solutions are:
-5.15 and 0.15