Question 38596
In order to ADD fractions, you must have a common denominator.  This means a number that each of the denominators divides evenly into.  You need to find a number that 3, 12, and 5 all divide evenly.  One way to do this is to take MULTIPLES of the largest number, which is 12, and keep going until you find a number that can be also divided by 3 and 5.  This means start with 12, 24, 36, 48, 60, etc.  Did you see that 60 can be divided by 3 and 5?  


Now, you need to change each fraction 1/3,   5/12,  and 4/5 into fractions whose denominator is 60.  To do this, the denominator 3 must be multiplied by 20, the denominator 12 must be multiplied by 5, and the denominator 5 must be multiplied by 12.  It looks like this:


{{{1/3 + 5/12 + 4/5}}}
{{{(1/3)*(20/20) + (5/12)*(5/5) + (4/5)*(12/12) }}}


What this means is that you have:
{{{20/60 + 25/60 + 48/60 }}}


Now add up all these numerators, and put the answer over the common denominator which is 60:

{{{ (20+25+48)/60}}}
{{{93/60}}}


The fraction reduces since you can divide both 93 and 60 by 3:
{{{31/20}}} 

This is an improper fraction, which is actually preferred in higher math, but in lower math they might want a mixed fraction.  You may want to write this as 
{{{1 }}}  {{{11/20}}}


R^2 at SCC