Let b be B

Let 2(3b)-20 be C

3b+b+2(3b)-20=180

10b=200

b=20

3b=60

2(3b)-20=100

Take each sentence and make an equation so you know what you are working with.

We know:

a+b+c=180

a=3b

c=2a-20.

So I will start with the last one because I can substitute for a.

c=2(3b)-20

6b-20=c

so now I have like terms (b) to put back into my orignal equation.

a+b+c=180

(3b)+b+6b-20=180

Simplify

10b-20=180

add 20 to each side

10b=200

divide by ten on each side

b=20

Now we can put b back into figuring out a and c…..

b=20

a=3b so therefore

a=60

c= 6b-20 6(20)-20=100

c=100

So a is 60, b is 20 and c is 100

Now to check

60+20+100=180 <--correct total

A=3b

B=B

C=2(3b)-20

so you now you gotta add ’em all up

3b + B + 2(3b) – 20 = 180 now, add up all your B’s

10b-20=180

10B = 200

B=20

A = 3B = 60

C = 2(3B)-20 = 2(60)-20 = 120-20 = 100

A = 60

B = 20

C = 100