It would be A. You can find this out by using SOH CAH TOA,
SOH means sin= opposite/hypotenuse
CAH mean cos= adjacent/hypotenuse
TOA means tangent= opposite/adjacent
You would use CAH since you are trying to find cos∠C
You would have cos∠C=10/26.
26 is the hypotenuse since it is opposite the right angle and is the biggest side.
10 is the adjacent since it is right next to C
You would simplify this down to 5/13 by dividing by 2.
This gives you A.
5 treats divided by six groups of one dog, or in easier terms, five dog treats divided up for 6 dogs. As a fraction, just remove the words except for 5, divided by, and 6, to give you 5/6. Hope this helped.
Ummmmmmmmmmmm your picture inst showing
A = D/BC. In order to isolate A, all you do is divide by BC
U probably need to add in a picture