Question

How many lb of brand X sugar which

Answer 1

Answer:  4 pounds of brand X sugar

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Reason:

n = number of pounds of brand X sugar

5n = cost of buying those n pounds, at $5 per pound

Brand Y costs $2 per pound, and you buy 8 lbs of it, so that's another 2*8 = 16 dollars.

5n+16 = total cost of brand X and brand Y combined

n+8 = total amount of sugar bought, in pounds

3(n+8) = total cost because we buy n+8 pounds at $3 per pound

The 5n+16 and 3(n+8) represent the same total cost.

Set them equal to each other. Solve for n.

5n+16 = 3(n+8)

5n+16 = 3n+24

5n-3n = 24-16

2n = 8

n = 8/2

n = 4 pounds of brand X sugar are needed

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Check:

n = 4

5n = 5*4 = 20 dollars spent on brand X alone

16 dollars spent on brand Y mentioned earlier

20+16 = 36 dollars spent total

n+8 = 4+8 = 12 pounds of both types of sugar brands combined

3*12 = 36 dollars spent on both types of sugar brands

The answer is confirmed.

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Another way to verify:

5n+16 = 3(n+8)

5*4+16 = 3(4+8)

20+16 = 3(12)

36 = 36