17 - 6 x 10/2 + 12 =
17 - 60/2 + 12 =
17 - 30 + 12 =
-13 + 12 =
-1 <==
750 kilometers. 21 divided by 7 is 3. If 7 cm equals 250 km, then 7 × 3 = 250.
3x-13=305
3x=305+13
3x=318
(3x)÷3=318÷3
x=106
check.. (3×106)-13=305
318-13=305
305=305
Cost of chicken wings at Buffalo Bills = 8 wings for $7
Cost of 1 wing at Buffalo Bills = 
Cost of chicken wings at Buffalo Mild Wings = 12 wings for $10
Cost of 1 wing at Buffalo Mild Wings = 
Cost of chicken wings at Wingers = 20 wings at $17
Cost of 1 wing at Wingers = 
Hence, comparing all the three costs per wing, we can see that Buffalo Mild Wings is serving chicken wings at lowest price of $0.833 per wing.