Answer:
Step-by-step explanation:
Let's convert this statement into a system of two equations
3 * (cost of a liter of milk) + 5 * (cost of a loaf of bread) = $11
4 * (cost of a liter of milk) + 5 * (cost of a loaf of bread) = $10
cost of a liter of milk = x
cost of a loaf of bread = y
3x + 5y = 11
4x + 4y = 10
You can now solve this using either substitution or elimination
I'll use elimination. Let's say I want to get rid of the x first. I need to choose numbers to multiply by the top and bottom equations to eliminat the x's. The easiest way to do this is to multiply them by each other. So we'll multiply the top by 4 and the bottom by 3. We'll need to make sure the signs are opposite as well so I'll make that a negative 3 on the bottom.
4 * (3x + 5y = 11)
-3 * (4x + 4y = 10)
12x + 20y = 44
-12x - 12y = -30
Now add straight down
0x + 8y = 14
8y = 14
y = 14/8 = $1.75
Now we can plug this back in to either equation to find the x. I'll choose the second equation
4x + 4*(1.75) = 10
4x + 7 = 10
4x = 3
x = 3/4 = $0.75
So, cost of a liter of milk = x = $0.75
and cost of a loaf of bread = y = $1.75
I=10/3......is your answer
Number of ways of picking a smaller number out of a bigger number is called combination.
Number of way of picking 3 stamps out of 4 is 4C3 (4 combination 3) = 4! / (3! x (4 - 3)!) = 4! / (3! x 1!) = (4 x 3 x 2 x 1) / (3 x 2 x 1 x 1) = 24 / 6 = 4 ways.
