Acircuit is supplied with 30 vdc and contains three resistors connected in series. the value or r1 is 80 , the value of r2 is 1,000 , and the value of r3 is 4,200 . what is the voltage drop across r2?

The answer is 5.68 Volts.

So givens are electric supply of 30 VDC and the values of 3 resistors. 

Given:
E= 30 VDC
R1 = 80 Ohms
R2 = 1000 Ohms
R3= 42000 Ohms

And what we are looking for is the voltage on the second resistor.
First we have to get the current of the circuit.

I = E/(R1+R2+R3)
I = 30 / (80+1000+4200)
I = 30 / (5280)
I = 0.00568 A

Then get the voltage V = I x R

V = 0.00568 x 1000
V = 5.68 V