Find the sum -3/5+4/9
answer with supporting work

Ok so to find the answer to this you have to make both fractions have the same denominator. 

To find the LCD (Least common denominator) follow these steps:

*Think: what number can be divided by both 9 and 5?

The answer is: 45 (shortcut way is to multiply both denominators by each other ie: 9 x 5)

Now make the numerators match:

For -3/5, the denominator (5) is multiplied by 9 to get 45, so the numerator (-3) has to also be multiplied by 9. 

You get: -27/45

For 4/9, the denominator (9) is multiplied by 5 to get 45, so the numerator (4) has to also be multiplied by 5.

You get: 20/45

Now the problem looks like this:

-27/45 + 20/45

**Be sure to remember there is a negative sign!

Now we just add the numerators:

-27 + 20 = -7

(If you have trouble doing that remember that you can just subtract the positive number from the negative ie: 27-20 and then just re-add the negative sign)

Then just re-add the denominator:

-7/45

This cannot be simplified so this is the final answer!

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