A child good at sums的用法和样例：
- The boy is good at doing a sum in his head.
- Teacher proposal: Parents should let the convention with child good nurturance, know courtesy, love thinks, dare and be good at expression.
- But experts say parents and teaching (teachers) may begin to suspect the problem, if a child is good at speaking, reading, and writing was (but) slow to develop math skills.
- The boy good at doing a sum in his head.