Jar B has 28 + 12 = <<28+12=40>>40 marbles.

Jar C has 2 x 40 = <<2*40=80>>80 marbles.

Therefore, there are 28 + 40 + 80 = <<28+40+80=148>>148 marbles altogether.

# Answer

148
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Jar A has 28 marbles. Jar B has 12 more marbles than jar A. Jar C has twice as many marbles as jar B. How many marbles are there altogether?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
148
Jar A has 28 marbles. Jar B has 12 more marbles than jar A. Jar C has twice as many marbles as jar B. How many marbles are there altogether?
train