
Suresh P. answered 04/24/13
Friendly, patient tutor with experience in many subjects!
Hey Hillary,
To solve this, there are several things to do to simplify the way this equation looks. First off, we need to make it so that the fractions can be added and subtracted across the equal sign as in any other equation. In order to do that, we need to find a common denominator - preferably the lowest one.
Even before we get to that step, it would be even more handy to convert the mixed numbers into simple fractions.
SO, starting with -4 1/10: We want to make this into a fraction that's easy to work with, such as 3/4 or 1/2. We know that 4 is equal to forty tenths, or 40/10 (ten tenths = 10/10 = 1, so 40/10 = 4), and there is 1/10 left over from the given equation. We simply add that 1/10 to 40/10. Therefore, 4 1/10 becomes 41/10, and we throw on the negative sign that they gave.
Now we have z + (-3 2/5) = -41/10.
So let's convert -3 2/5 into a simple fraction with a denominator of 10 -- combining the first two steps I mentioned way above. That way we can add or subtract the two fraction across the equal sign, leaving z all by itself and solving the equation. Starting with the 2/5 part, we can multiply the whole thing by 2 to give us 4/10, which is still reducible to 2/5 (meaning we haven't changed anything about the value of the mixed number). We know that thirty tens make up 3 (30/10 = 3), and we had the 4/10 from just before, so 30/10 + 4/10 = 34/10. Therefore, 3 2/5 = 34/10. And we'll throw on the negative sign they gave once again.
After all that, we now have z + (-34/10) = -41/10, which now is simple algebra.
To isolate the z, we have to add positive (34/10) to both sides and cancel it out on the left. Also note that we can add the fractions now because they have the same denominator: 10.
-41/10 + 34/10 = -7/10
Hope this helped! Remember that whenever you are performing operations with mixed numbers or fractions with different denominators, it is important to convert one or both so that they share a common denominator (e.g. 2/5 + 3/4 becomes 8/20 + 15/20).