Which expression will help you find the measure of angle R?

Since you don't have a right triangle, you can't use just sin, cos, or tan

Either use the Law of Cosines (if you have SAS or SSS) or otherwise use the Law of Sines.

Since you don't have either SAS or SSS, use the Law of Sines.

   sin(R) / r  =  sin(Q) / q                           

   sin(R) / 3.5  =  sin(70°) /6.2                       

This is as far as you have to go, but you could finish it:

   sin(R)  =   sin(70°) /6.2 x 3.5

     R  =  invSin(  sin(70°) /6.2 x 3.5 )

Hey, Tori...... it's "D"......the Law of Sines says:

Sine of an angle/ It's opposite side = Sine of another angle/It's opposite side