Ineed the answer with at least a decent explanation. and quickly.

answer is D

Step-by-step explanation:

If AB and AC are the same that means that <B and <C are the same and since all sides must add up to 180 degrees then you add angles C and B together and subtract by 180.

180-80=100

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb

idc

step-by-step explanation:

idk