From the graph:

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The library of congress has 28.7 millions of volumes.

The Harvard University has 14.7 millions of volumes.

Let n represent the number of more volumes the library of congress had  than the Harvard University.

Write the verbal expression to represent the situation.

Rewrite the equation: \ \

\

According to subtraction property of equality: a = b, then a c = b c

\

  n = 28.7 14.7                           (Additive inverse property:14.7 14.7 = 0)

 n = 14                                    (Add:28.7 14.7 = 14)

The library of congress has 14 more millions of volumes than the Harvard

University.