If you change the fractions into decimals, 5/6=.83, 2/3=.67, 3/4=.75, you can see that 2/3 is the shortest
You need this key result: in any polygon, the sum of the interior angles is

where
is the number of sides of the polygon.
Your polygon has seven sides, and the measures of all angles are given. So, we can write

Again, we've simply written that the sum of all interior angles is the number of sides, minus two, times 180.
We can simplify both sides: we sum like terms on the left hand side, and we easily compute the right hand side:

and we can solve this equation for
by dividing both sides by 30:

Finally, the required angles is 
Answer:
n=42
Step-by-step explanation:
n/6-2=5
n/6=7
n=42
His basic salary is $ 2,500, his commission on sales is 3% (on sales only)
At the end of te month he got $3,040
Let x be the TOTAL sales performed during this month, so the money generated from sales (only) is (x).(3%), Hence the equation:
2500 + (x).(3%) = 3040
2500 + x(0.03) = 3040
x(0.03) = 3040-2500
x(0.03) = 540
and x = 540/0.03
x = $18,000