Answer : 29.5°
Given r = 10, q = 20, and Q = 100°
From the attached figure we can see that two sides and one angle is given
We use sine rule to find angle R
![(sin A)/(a) = (Sin B)/(b) = (Sin C)/(c)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/hfqxc3bxf2eunvu40ztvtkx1pbltojh7do.png)
In triangle QRS
![(sin Q)/(q) = (Sin R)/(r) = (Sin S)/(s)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/4yogisb6c9bmo2uhebwullp43soqv6mhyj.png)
r = 10, q = 20, and Q = 100°
![(sin Q)/(q) = (Sin R)/(r)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/8w6x46o440oafapuwbue0xzsnsr6bijsds.png)
Replace all the values
![(sin 100)/(20) = (sin R)/(10)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/3oabpf3najg7ddyb0e5vsd8018s5fulv16.png)
![(sin(100)*10)/(20) = sin(R)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/c5hswmgtqjbqelbcv8mllo4ruadsgco8i5.png)
=sin R
0.4932403876 = sin (R)
R=
![sin^(-1) (0.4932403876)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/xzfmzjpmsowseqgwmuj41di5r3of9n8mdh.png)
R= 29.5 degrees