Find the resistance across

B and D.

In order to find the total resistance, first we need to memorize the rule which we have learned which is , THE POINTS WHOSE ACROSS WE HAVE TO EVALUATE THE TOTAL RESISTANCE ARE THE GIVEN POINTS AND WE CONSIDER OR IMAGINE THAT A BATTERY IS CONNECTED TO THE CIRCUIT THROUGH THESE TWO POINTS ONLY .

B and D are the given points in this part and the remaining are the simple points to deal with (that is A and C).

The resistors in the line BC are in series as well as the resistors in the line AD are also in series with each other, so by solving we get

Merge the point A into point B and also merge the point C into point D, all three resistors are parallel to each other, so,

These two resistors are parallel to each other, so by solving them we get,

Thus, it is the resultant or total resistance.