Not sure how I begin solving this. I'm supposed to draw the thevenin equivalent circuit for this (as well as Norton). I'm used to the source being a voltage, but I'm not sure how to deal with this one.

Do I first find the open-circuit voltage?

Someone has told me that the 0.5*30 = 15V. Then they used the voltage divider rule on the 40 ohms resistor multiplied by 15 to get the answer of 6V.

I don't understand why this is it. Could someone explain this to me?

Isn't the 0.5A source in parallel with a 30 ohms and 70 ohms resistors? So how is the voltage divider law done as though the resistors are in series..?

Thanks.