Answer
-29.7 cm
Work Step by Step
Use the lensmaker’s equation.
$$\frac{1}{f}=(n-1)(\frac{1}{R_1}+\frac{1}{R_2})$$
$$f=\frac{1}{n-1}(\frac{R_1R_2}{R_1+R_2})$$
$$f=\frac{1}{1.52-1}(\frac{(-33.4cm)(-28.8cm)}{ (-33.4cm)+(-28.8cm)})$$
$$f=-29.7cm$$