1. **State the problem:**
We have an outer rectangle with dimensions length $3x - 2$ and width $x + 6$, and an inner rectangle with dimensions length $2x$ and width $x - 1$. The shaded region is the area of the outer rectangle minus the area of the inner rectangle, which equals 103 ft².
2. **Write the formula for the shaded area:**
$$\text{Shaded area} = \text{Area of outer rectangle} - \text{Area of inner rectangle}$$
3. **Express the areas in terms of $x$:**
$$\text{Area of outer rectangle} = (3x - 2)(x + 6)$$
$$\text{Area of inner rectangle} = (2x)(x - 1)$$
4. **Set up the equation:**
$$ (3x - 2)(x + 6) - 2x(x - 1) = 103 $$
5. **Expand the terms:**
$$ (3x - 2)(x + 6) = 3x \cdot x + 3x \cdot 6 - 2 \cdot x - 2 \cdot 6 = 3x^2 + 18x - 2x - 12 = 3x^2 + 16x - 12 $$
$$ 2x(x - 1) = 2x^2 - 2x $$
6. **Substitute back into the equation:**
$$ 3x^2 + 16x - 12 - (2x^2 - 2x) = 103 $$
7. **Simplify the left side:**
$$ 3x^2 + 16x - 12 - 2x^2 + 2x = 103 $$
$$ (3x^2 - 2x^2) + (16x + 2x) - 12 = 103 $$
$$ x^2 + 18x - 12 = 103 $$
8. **Bring all terms to one side:**
$$ x^2 + 18x - 12 - 103 = 0 $$
$$ x^2 + 18x - 115 = 0 $$
9. **Solve the quadratic equation using the quadratic formula:**
$$ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} $$
where $a=1$, $b=18$, and $c=-115$.
10. **Calculate the discriminant:**
$$ \Delta = 18^2 - 4 \cdot 1 \cdot (-115) = 324 + 460 = 784 $$
11. **Find the roots:**
$$ x = \frac{-18 \pm \sqrt{784}}{2} = \frac{-18 \pm 28}{2} $$
12. **Calculate each root:**
- $$ x = \frac{-18 + 28}{2} = \frac{10}{2} = 5 $$
- $$ x = \frac{-18 - 28}{2} = \frac{-46}{2} = -23 $$
13. **Choose the valid root:**
Since dimensions must be positive, $x = 5$.
14. **Find the dimensions of the inner rectangle:**
- Length: $$ 2x = 2 \times 5 = 10 $$
- Width: $$ x - 1 = 5 - 1 = 4 $$
**Final answer:** The inside rectangle has dimensions length 10 ft and width 4 ft.
Rectangle Dimensions 430F37
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