Answer: 
Step-by-step explanation:
We have given the numbers = 2,0,1,9
We can use addition and subtraction operation to the given numbers such that the answer will be equals to 6.
We can add 2 ,0 and 1 and then subtract from 9 , we will get 6.
So the required expression can be

hence, the required expression can be 
Answer:
a= c/2
b= (c/2)×√3
side b is the side with the 60 degree angle.
side a is the side with the 30 degree angle.
using the theorem that the side with the 60 degree × 2 = length of side c and the side with the 60 degree × √3 = b.
I get the following equations shown above.
F=9/5c+32
-31=9/5c+32
-63=9/5c
-35=c