Question

1. tan x
2. tan a

Explanation:

Step1: Recall tangent - ratio formula

The tangent of an angle in a right - triangle is defined as $\tan\theta=\frac{\text{opposite}}{\text{adjacent}}$.

Step2: Find $\tan X$ for the first triangle

In the first right - triangle with respect to angle $X$, the opposite side to angle $X$ is $20$ and the adjacent side is $21$. So, $\tan X=\frac{20}{21}$.

Step3: Find $\tan X$ for the second triangle

In the second right - triangle with respect to angle $X$, the opposite side to angle $X$ is $21$ and the adjacent side is $28$. So, $\tan X = \frac{21}{28}=\frac{3}{4}$.

Step4: Assume the third triangle is for $\tan A$

In the third right - triangle with respect to an unnamed angle (assuming it is $A$), the opposite side to angle $A$ is $20$ and the adjacent side is $21$. So, $\tan A=\frac{20}{21}$.

Answer:

For the first triangle: $\tan X=\frac{20}{21}$
For the second triangle: $\tan X=\frac{3}{4}$
For the third triangle (assuming angle $A$): $\tan A=\frac{20}{21}$