Hi @Hamidaafrinheart,
The answer would be
![\boxed {37 \text { T-Shirts}}](https://img.qammunity.org/2019/formulas/mathematics/middle-school/yoojzo9owq86z5qhs04q9x2fim4bbp56d2.png)
In this problem we are being asked to determine the t shirts that Nathan needs to sell to get a bonus.
To solve this we simply need to add and subtract.
![23+15=38](https://img.qammunity.org/2019/formulas/mathematics/middle-school/rp94cv2z5w8wjisogomphrl87lwqbzhjz4.png)
Now, subtract this number from 75 to determine the amount of T-Shirts that still need to be sold.
![75-38=37](https://img.qammunity.org/2019/formulas/mathematics/middle-school/nuzun0kaq5rr4byncm18v9gc9flslo3k42.png)
Nathan needs to sell 37 T-Shirts to get a bonus.
![\boxed {37 \text { T-Shirts}}](https://img.qammunity.org/2019/formulas/mathematics/middle-school/yoojzo9owq86z5qhs04q9x2fim4bbp56d2.png)
Let me know if you have any further questions!
@MythicalPanda