5 x 4 = 20
7 x 4 = 28
5:7 = 20:28
When you multiply both by 4, they equal the outcome on their side of the function, making them equivalent
(Sorry if function isn't the right word)
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The answer is C Radius because look o. the outside it's clearly bigger
Simple...
you have

and

Just subtract...but first find a common denominator...
Use 40 as the common denominator...

and

So, subtract,

=

Thus, your answer.