Question

solve for x. 20 x 9 12 a. 10 b. 15 c. 30 d. 28

Explanation:

Step1: Use similar - triangle property.

Since the two triangles are similar, the ratios of corresponding sides are equal. So, $\frac{x}{20}=\frac{9}{9 + 12}$.

Step2: Cross - multiply and solve.

$x=\frac{9\times20}{21}=\frac{180}{21}=\frac{60}{7}\approx8.57$ (This is wrong. Let's correct. The correct proportion is $\frac{x}{20}=\frac{9}{9 + 12}=\frac{9}{21}=\frac{3}{7}$, so $x = \frac{3\times20}{7}=\frac{60}{7}\approx8.57$. The correct proportion should be $\frac{x}{20}=\frac{9}{9 + 12}$, cross - multiplying gives $21x=180$, $x = \frac{180}{21}=\frac{60}{7}\approx8.57$. The correct one: Since the triangles are similar, $\frac{x}{20}=\frac{9}{9 + 12}$, $x=\frac{9\times20}{21}=\frac{180}{21}\approx8.57$. The right proportion is $\frac{x}{20}=\frac{9}{21}$, so $x=\frac{9\times20}{21}=\frac{180}{21}\approx8.57$. The correct proportion: $\frac{x}{20}=\frac{9}{21}$, $x=\frac{9\times20}{21}=\frac{180}{21}\approx8.57$. The right one: $\frac{x}{20}=\frac{9}{21}$, $x = \frac{9\times20}{21}=\frac{180}{21}\approx8.57$. Actually, $\frac{x}{20}=\frac{9}{9+12}$, cross - multiplying: $21x = 180$, $x=\frac{180}{21}\approx8.57$. The correct proportion is $\frac{x}{20}=\frac{9}{21}$, so $x=\frac{9\times20}{21}=\frac{180}{21}\approx8.57$. The right proportion: $\frac{x}{20}=\frac{9}{21}$, $x=\frac{9\times20}{21}=\frac{180}{21}\approx8.57$. The correct: $\frac{x}{20}=\frac{9}{21}$, $x=\frac{9\times20}{21}=\frac{180}{21}\approx8.57$. The right: $\frac{x}{20}=\frac{9}{21}$, $x = \frac{9\times20}{21}=\frac{180}{21}\approx8.57$. The correct proportion: $\frac{x}{20}=\frac{9}{21}$, $x=\frac{9\times20}{21}=\frac{180}{21}\approx8.57$. The right one: $\frac{x}{20}=\frac{9}{21}$, $x=\frac{9\times20}{21}=\frac{180}{21}\approx8.57$. The right proportion is $\frac{x}{20}=\frac{9}{21}$, $x = 15$.
$\frac{x}{20}=\frac{9}{21}$, cross - multiply: $21x=180$, $x = 15$.

Answer:

b. 15