I want to say C, but im not completely positive :/ sorry. C sounds right though. Hope this helps!
The measure off DF is 11.
In a circle inscribed within a triangle, the distance from each vertex of the triangle to the two nearest touchpoints (points of tangency on the circle) are equal. Since SD=4, DT=4 as well. Since UF=7, then FT=7.
DF=DT+TF=4+7=11.
Answer:
Step-by-step explanation:




do cross multiplication

4x + y = 12
Get y by itself
Subtract 4x
y = -4x + 12
Since you know what y is, you can plug the value into the second equation
6x + 2(-4x + 12) = 18
6x - 8x + 24 = 18
-2x = -6
x = 3
Plug the value 3 into x for y = -4x + 12 in order to find y
-4(3) + 12 = y, y = 0
Solution: x = 3, y = 0