What's happening is that every subtraction can be written as "addition of the opposite."
18-5 = 18 + (-5)
One reason this is done in the work you showed is that they're trying to show why you distribute the negative and the 1 into the parentheses, why you multiply everything in the parentheses by "-1" and not just 1.
The other reason is to later to be able to move the individual terms around, so you'll be able to combine like terms.
When you move terms around, the sign has to stay attached to the term, so writing all the subtractions as addition helps keep the sign attached.
50 + 20h = 100 + 10h
20h - 10h = 100 - 50
10h = 50
h = 50/10
h = 5 <== they will charge the same at 5 hrs
8 in 2.408 is closer to 10, so you round 2.408 to 2.41
Using scientific notation, it is found that:
67 ns = 
s
<h3>What is scientific notation?</h3>
A number in scientific notation is given by:
With the base being 
.
In this problem, the amount is of 67 ns.
Each ns has 
seconds, hence:
We want the base between 1 and 10(exclusive), hence, we move the decimal digit one digit to the left and add one to the exponent, and the representation is:
67 ns = s
You can learn more about scientific notation at brainly.com/question/16394306
Answer:
88°?
Step-by-step explanation:
