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?
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.
#### 148