Answer: 
Work Shown:

This can be rewritten into 
10% of 26.80 = 2.68
5% of 2.68 = 1.34
2.68 + 1.34 = 4.02
Your best estimate is 4.05
No, the longest side must be less than the sum of the smaller sides or else they won't connect (try it yourself with straw or something)
40+30>120
70>120
false, therfor they canonot be a triangle
Answer:
$1350
Step-by-step explanation:
Percentage commision earned = 10%
Amount needed to pay for concert = $135
Hence, total sales for the week must be :
Let total sales = x
10% of total sales = $135
10/ 100 * x = $135
0.1x = $135
x = $135 / 0.1
x = $1350