Question

$\triangle abd \cong \triangle cdb$. find y.
$ab = 7y$
$dc = 3y + 20$

Explanation:

Step1: Identify congruent sides

Corresponding sides of congruent triangles are equal, so $AB = DC$.

Step2: Set up equation

Substitute side expressions: $7y = 3y + 20$

Step3: Solve for y

Subtract $3y$ from both sides: $7y - 3y = 20$
Simplify: $4y = 20$
Divide by 4: $y = \frac{20}{4}$

Answer:

$y = 5$