Question

lesson 18 | session 2
3 nodin makes soap sculptures of sea turtles. each sculpture weighs $\frac{3}{8}$ pound. he ships them in a wooden box that weighs 2 pounds. the total weight of the box filled with $t$ sea turtles is 5 pounds. how many sea turtles are in the box? show your work.
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4 solve $-0.4k - 6 = 1.2$. show your work.
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5 claudia buys 12 postcards, 12 stamps, and 1 pen. the postcards cost twice as much as the stamps. the pen costs $1.50. the total cost is $14.10. how much does each postcard cost? show your work.
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Explanation:

Problem 3

Step1: Set up weight equation

Let $t$ = number of turtles. Total weight: $2 + \frac{3}{8}t = 5$

Step2: Isolate the variable term

$\frac{3}{8}t = 5 - 2$
$\frac{3}{8}t = 3$

Step3: Solve for $t$

$t = 3 \div \frac{3}{8} = 3 \times \frac{8}{3}$
$t = 8$

Problem 4

Step1: Isolate the variable term

$-0.4k = 1.2 + 6$
$-0.4k = 7.2$

Step2: Solve for $k$

$k = 7.2 \div (-0.4)$
$k = -18$

Problem 5

Step1: Define cost variables

Let $s$ = cost of 1 stamp, so $2s$ = cost of 1 postcard.

Step2: Set up total cost equation

$12(2s) + 12s + 1.50 = 14.10$
$24s + 12s + 1.50 = 14.10$

Step3: Simplify and isolate $s$

$36s = 14.10 - 1.50$
$36s = 12.60$
$s = \frac{12.60}{36} = 0.35$

Step4: Find postcard cost

Postcard cost = $2s = 2 \times 0.35$
Postcard cost = $0.70$

Answer:

1. Number of sea turtles: 8
2. Value of $k$: $-18$
3. Cost of each postcard: $\$0.70$