We know sum of interior angles in any triangle is 180°. Your specific triangle is a right triangle (one angle must be 90°) and we are also given another angle (57°) that means we can find angle T,
![T=180^(\circ)-90^(\circ)-57^(\circ)=33^(\circ)](https://img.qammunity.org/2021/formulas/mathematics/high-school/urdgpf95mif6f8m4z3perom6zutv9l1e8c.png)
Use the sine function to find
,
![\sin(57^(\circ))=15/RT\implies RT=15/\sin(57^(\circ))\approx17.9](https://img.qammunity.org/2021/formulas/mathematics/high-school/lu11vg2vy9fampt5f19w2lyr1myydbbohk.png)
Use the tangent function to find
,
![\tan(57^(\circ))=15/RS\implies RS=15/\tan(57^(\circ))\approx9.7](https://img.qammunity.org/2021/formulas/mathematics/high-school/ieb4jagze01vtwf8db0f00o0pabyil7opq.png)
Hope this helps.