Question number 7, how to calculate the equivalent resistance of the combination of resistors.

-- On the upper path, the 3 and the 4 are in series, so they look like 7 ohms.

-- On the lower path, the 5 and the 6 are in series, so they look like 11 ohms.

-- Now you have 7 ohms in parallel with 11 ohms. Can you do that ?

It's 4.28 ohms.

the second one and the forth one are in the purple because they are opinions and the rest are in the yellow

explanation:

it doesn't. it was imagined up in the middle ages.