Well, since 3 candles are 19.50, simply divide. This will make a ratio so that 1 candle will equal 6.50 per candle.
19.50 / 3 candles = 6.50 per candle.
6) check picture
a) all three lines are parellel and have the same slope. the only difference is that they are translated on different points on the x-axis.
not sure about the rest sorry :(