Answer:
Let the number of people that wore black pants be
![=x](https://img.qammunity.org/2023/formulas/mathematics/college/1ye1eo60321kt0irebsbvlxoc6mkb0xjkb.png)
Let the number of people who wore blue pants be
![=y](https://img.qammunity.org/2023/formulas/mathematics/high-school/eyqg7ht214ag7yrcgx5vsdv0indwor49dl.png)
The total number of students in the choirs is
![=44](https://img.qammunity.org/2023/formulas/mathematics/college/scjccb7xci1orydhuvbi2e81ao33u5881c.png)
Three times as many students wore black pants as blue jeans can be represented below as
![x=3y\ldots\text{.}(1)](https://img.qammunity.org/2023/formulas/mathematics/college/k597udysbe58dh5nffows5agj84n43vno7.png)
The total number of students will be represented below as
![x+y=44\ldots\ldots(2)](https://img.qammunity.org/2023/formulas/mathematics/college/xrda39cyux2o688f92ef77d6831gic44bm.png)
Substitute the equation (1) in equation (2)
![\begin{gathered} x+y=44\ldots\ldots(2) \\ x=3y\ldots\text{.}(1) \\ 3y+y=44 \\ 4y=44 \\ \text{divide both sides by 4} \\ (4y)/(4)=(44)/(4) \\ y=11 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/gkfq8pkhvaxt19commfdrbmq3snrp5xcle.png)
Hence,
The number of students who wore blue pants is =11
The right answer is OPTION D