a. [tex]11.28\Omega[/tex]
The equivalent resistance of a series combination of two resistors is equal to the sum of the individual resistances:
[tex]R_{eq}=R_1 + R_2[/tex]
In this circuit, we have
[tex]R_1 = 7.25 \Omega\\R_2 = 4.03 \Omega[/tex]
Therefore, the equivalent resistance is
[tex]R_{eq}=7.25 \Omega + 4.03 \Omega=11.28 \Omega[/tex]
b. 5.8 V, 3.2 V
First of all, we need to determine the current flowing through each resistor, which is given by Ohm's law:
[tex]I=\frac{V}{R_{eq}}[/tex]
where V = 9.00 V and [tex]R_{eq}=11.28 \Omega[/tex]. Substituting,
[tex]I=\frac{9.00 V}{11.28 \Omega}=0.8 A[/tex]
Now we can calculate the potential difference across each resistor by using Ohm's law again:
[tex]V_1 = I R_1 = (0.8 A)(7.25 \Omega)=5.8 V[/tex]
[tex]V_2 = I R_2 = (0.8 A)(4.03 \Omega)=3.2 V[/tex]