Вычислим:

1. 
   

   $$300 - (90+70) + (86-46) = 300 - 160 + 40 = 140 + 40 = 180$$

   
   


2. 
   

   $$90:(10 \cdot 9):(9:9) = 90:90:1 = 1:1 = 1$$

   
   


3. 
   

   $$0 \cdot 8 + 7 = 0 + 7 = 7$$

   
   


4. 
   

   $$0 \cdot (8+7) = 0 \cdot 15 = 0$$

   
   


5. 
   

   $$91:13 \cdot 7 = 7 \cdot 7 = 49$$

   
   


6. 
   

   $$84:(14 \cdot 3) = 84:42 = 2$$