A proportion is an equal ratio (or fraction)
18 divided by 18 is 1
72 divided by 18 is 4
so a proportion of 18:72 is 1:4
Both of those values are in scientific notation
Scientific notation is when we have numbers of the form
where
and b is an integer.
Both 9.725 and 9.7250 are inside the inequality mentioned above.
Scientific notation is used to help describe very large numbers, or very small numbers, depending on context.
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If you wanted to convert from scientific notation to standard notation, then you'll move the decimal point based on what the exponent is. The positive 6 means we move the decimal point 6 places to the right.
We go from 9.725 to 9,725,000 which is about 9.7 million
In other words, 
As another example,
since we start at 1.23 and move the decimal point 11 spots to the right to arrive at 123,000,000 aka 123 billion.
0.4 is the divisor, or whichever number is under the fraction. This is because the denominator of any fraction is always the divisor of the numerator of the fraction.
Answer:
y=0.75x + 1.25
Step-by-step explanation:
You just need to isolate y by transferring all the numbers to the other side of the equation (& the numbers with x)
Glad to help