You use a closed dot with the greater than or less than with the line under the symbol or the greater than or equal to or the less than or equal to symbols. The line indicates a closed dot.
It Is Just -1.
The Parenthesis Are All Simplified, And The Subtraction Sign Changes It To Negative. So, 1 Changed To Negative Is -1. <span />
You have two totals: total # of bills and total amount of $. Using x as #of 20s, and y as # of 50s, you can use the system
x+y=18
20x+50y=450
Answer
<2 = <4 = <6 = <8
All of those are 94 degrees
<1 = <3 = <5 + <7
All of those are 86 degrees
Hope this helps :D