6 : 2/3.....multiply by 3
18 : 2...reduce
9:1 or 9/1
The number of ways to choose the colors is 36
<h3>How to determine the number of ways?</h3>
The given parameters are:
Colors = 9
Colors to choose = 7
Since order does not matter, then it is combination
This is calculated using:

This gives

Evaluate

Hence, the number of ways is 36
Read more about combination at:
brainly.com/question/11732255
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16/2
According to PEMDAS
Multiplying/dividing comes first when you read the equation from left to right
Let x = discount rate
Equate:
$80(1-x) = $60
Solve for x:
1-x = 60/80
1-x = 3/4
x = 1 - 3/4
x = 1/4 or 0.25
x = 25%