Answer:
Perimeter of △BDC=Sum of all the sides=BD+DC+CB=15+15+15=45
Step-by-step explanation:
Given ΔABC is an isosceles triangle, thus, AB=BC=x and AC=12,
perimeter of △ABC is=42
⇒x+x+12=42
⇒2x=30
⇒x=15
Thus, AB=BC=15
Now, △BDC is an equilateral triangle therefore BD=DC=BC=x
Since, x=15, therefore BD=DC=BC=15
Now, Perimeter of △BDC=Sum of all the sides=BD+DC+CB=15+15+15=45
