\( \Large 39.8\% \   of \  400 + ?\% \   of \   350 = 230 \)

\( \Large 159.2 + \frac{350 \times ?}{100} = 230 \)

\( \Large = ? = \left(230 - 159.2\right) \times \frac{100}{350} = 20.23 = 20 \)