Please hellp with this geometery

45 cm

Step-by-step explanation:

Δ ABC is isosceles with AC, the base thus AB = BC

Perimeter = 42 and AC = 12, thus

AB + BC = 42 - 12 = 30, hence

AB = BC = 30 ÷ 2 = 15

Δ BDC is equilateral, thus has 3 congruent sides

The sides each have a measure of 15 cm ( since BC = 15 ), thus

perimeter of Δ BDC = 3 × 15 cm = 45 cm

i would have to say it is c.

-4

step-by-step explanation:

do 6-10=

if u need it to be negative.