The equivalent capacitance of the system shown in the following...

For parallel grouping(the loop part), equivalent capacitance can be written as

${C}_{p} = \left(3 + 3\right)\mu F = 6\mu F$.

Now, this part is in series with the left capacitor. So we can write

${C}_{eq} = \left(\dfrac{3 \times 6}{3 + 6}\right)\mu F = 2\mu F$