Please assist me with these story problems.

  4. 16

  5. $88

  6. $687.50

Step-by-step explanation:

4. Let n represent the number.

An expression representing the number multiplied by 0.9 and 6.3 subtracted from the product is ...

  0.9n -6.3

We want that result to be 4.5, so we have the equation ...

  0.9n -6.3 = 4.5

Since all of the coefficients are divisible by 0.9, we can divide by 0.9 to get ...

  n -7 = 9

Adding 7 gives ...

  n = 16

The number is 16.

5. For a problem like this, I like to work it backward. If Craig got an extra $18, then everyone's share was $32 -18 = $14. That was the share from a 5-way split, so the amount the friends split evenly was 5×$14 = $70. The total they started with must have been $70 +18 = $88.

The amount they split unevenly was $88. The amount they split evenly, after setting aside $18 for Craig's parents, was $70.

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It is a bit tricky to write one equation for the amount the friends started with before they did any splits. Call that amount A. Then after setting aside $18, they split (A-18) five ways. Each of those splits was then (A-18)/5. When the $18 was added to one of those, the result was the $32 that Craig got. So, we have ...

  (A -18)/5 +18 = 32

and the solution process is similar to the "working backward" description above: subtract 18, multiply by 5, add back 18.

  (A -18)/5 = 14

  A -18 = 70

  A = 88 . . . . . . . . the amount the friends split unevenly

6. Let P represent the original price of the laptop. We're told the price after all of the discounts was 500, so we have ...

  P -50 -(0.20P) = 500

  0.80P = 550 . . . . . add 50, collect terms

  P = 687.50 . . . . . . . divide by the coefficient of P

The original price was $687.50.

7. d. 64

8. i. 32

9. c. 125

10. j. none of the above

11. d. 81

12. i. 216

13. e. none of the above

14. g. 240

15. e. none of the above

16. g. 32

17.   e. none of the above