Question 24148
fractions are very difficult for most people.  Don't feel discouraged.  It seems to be one of the hardest things for people even in the higher math classes.

for your equation, you must find the common denomonator before you can add or subtract a fraction.  Always remember this.  when you add or subtract, the number on the bottom must be the same.  If it is not, you must make it that way.  If you do not know how to do this. It is most important that you review how to do this. I can give you a short cut, but your instructor may not approve of your using it. So it is best you learn the hard way first.  Email me if you want a lesson on the short cut at athompson022@nttc.edu.

Ok lets try to work your question.
you have
7/4+(-1/3)
first you must think of the smallest number both 4 and 3 will go into.  I would say that would be 12.  to get 12 in the first fraction you would have to multiply the 4 by 3 on the bottom, so you must use the same number to multiply on the top. that means you multiply the 7 by 3 as well.  In the second fraction you would multiply the 3 by a 4 to get 12 so you would do the same to the top multiplying the 1 by 4 as well.  your new equation with a common denomonator would be
21/12+(-4/12)  pleasw notice that if you were to reduce these you would get  
               your origional equation.  So you know you are right.
Now all you have to do is subtract 4/12 from 21/12 and reduce if you can
21/12-4/12=17/12

17 is prime so there is no reduction.
17/12 is your answer.

I hope this helps.  There is a shortcut, but your instructor will probably not approve until you reach the college level.  I will be happy to give it to you though if you email me.
A.