Answer
Another capacitor may be wired/soldered in series with the 2900 pF capacitor to lower the overall capacitance, i.e., to make the equivalent capacitance equal to 1200 pF.
Work Step by Step
When capacitors are wired in series, we use equation 19–6 to find the equivalent capacitance.
$$\frac{1}{C_{eq}}=\frac{1}{1200\times10^{-12}F}=\frac{1}{2900\times10^{-12}F}+\frac{1}{C}$$
$$C=2.047\times10^{-9}F\approx 2 nF$$
We should solder a 2 nF capacitor in series with the 2900 pF capacitor. We will have to break at least one existing connection to add the capacitor in series.