This functional magnetic resonance imaging (fMRI) study examined neural contributions to managing task difficulty and response correctness during fluid reasoning. Previous studies investigate reasoning by independently varying visual complexity or task difficulty, or the specific domain. Under natural conditions these factors interact in a complex manner to support dynamic combinations of perceptual and conceptual processes. This study investigated fluid reasoning under circumstances that would represent the cognitive flexibility of real life decision-making. Results from a mixed effects analysis corrected for multiple comparisons indicate involvement of cortical and subcortical areas during fluid reasoning. A 2 x 2 ANOVA illustrates activity related to variances in task difficulty correlated with increased blood oxygenation level-dependent (BOLD)-signal in the left middle frontal gyrus (BA6). Activity related to response correctness correlated with increased BOLD-signal in a larger, distributed system including right middle frontal gyrus (BA6), right superior parietal lobule (BA7), left inferior parietal lobule (BA40), left lingual gyrus (BA19), and left cerebellum (Lobule VI). The dissociation of function in left BA 6 for task difficulty and right BA6 for response correctness and the involvement of a more diffuse network involving the left cerebellum in response correctness extends knowledge about contributions of classic motor and premotor areas supporting higher level cognition.