How do you solve #\frac { 7} { n + 3} = \frac { 3} { 9}#?

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Answer 1 · 2017-07-20T01:33:08

Simply cross multiply.

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As you can see in my explanation we first start off by cross multiplying:

#9*7=63# and #3(n+3)=3n+9#

We then subtract the #9# to get #3n# alone:

#63-9=54#

Then we simply divide by #3# to get #n# alone:

#54/3=18#

Therefore, our answer is #n=18#.

However, if this is true, when you cross multiply again, they should be the same number.

#7*9=63#
#18+3=21*3=63#

They check out, so this answer is valid and correct.