The complete solution is in image attached.
You could set up a ratio:

which then becomes:
Answer:
I know the top one is correct so the bottom has to be as well. :)
The square root of 5 is the positive real number that, when multiplied by itself, gives the prime number 5. It is more precisely called the principal square root of 5, to distinguish it from the negative number with the same property
hope it helps
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