Answer:
Explanation:
The total number of shirts that the school club sold is 300.
31% were sold to fifth graders. This means that the number of shirts that were sold to fifth graders is 
31/100 × 300 = 0.31 × 300 = 93
52% were sold to sixth graders. This means that the number of shirts that were sold to sixth graders is 
52/100 × 300 = 0.52 × 300 = 156
The total number of shirts sold to fifth graders and sixth graders is 
93 + 156 = 249
The number of shirts sold to teachers is 
300 - 249 = 51