Answers:
- Total equation: x+y = 80
- Legs equation: 2x+4y = 248
- How many ducks? 36
- How many cows? 44
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Further explanation:
- x = number of ducks
- y = number of cows
x+y = 80 is the total equation (ie the head count equation) since we assume each animal has 1 head, and there are 80 heads total.
That equation can be solved to y = 80-x after subtracting x from both sides.
The legs equation is 2x+4y = 248 because...
- 2x = number of legs from all the ducks only
- 4y = number of legs from all the cows only
- 2x+4y = total number of legs from both types of animals combined
We're told there are 248 legs overall, so that's how we ended up with 2x+4y = 248
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Let's plug y = 80-x into the second equation and solve for x.
2x+4y = 248
2x+4( y ) = 248
2x+4( 80-x ) = 248
2x+320-4x = 248
-2x+320 = 248
-2x = 248-320
-2x = -72
x = -72/(-2)
x = 36
There are 36 ducks
Now use this x value to find y
y = 80-x
y = 80-36
y = 44
There are 44 cows.
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Check:
36 ducks + 44 cows = 80 animals total
36*2 + 44*4 = 72 + 176 = 248 legs total
The answers are confirmed.
I believe it is 3x+21 but i could be wrong :/ my explaination is -3 • -X would be +3x because it was distributed and -3 • -7 would be +21
The best way to go about this questions is to write out a formula in which x represents the original price of the dress: x*0.90=27. To see where the 0.90 came from, if Kate's dress was 10% off, she must have paid 90% of the original price (100%-10%=90%). Then, to convert a percentage to a decimal, move the decimal point twice to the left so 90% becomes 0.90. Then, our formula essentially means that 90% of some number (x) is equal to 27. To solve for x, divide both sides of the formula by 0.90 to get x=$30 which is the final answer.
I hope this helps.
