Question 132432
The best way is to change your mixed fractions to improper fractions (mixed fractions are a combination of a whole number and a fraction, and improper fractions are fractions that have a numerator, top number, larger than the denominator, or bottom number)


One unit or 1 is the same as {{{5/5}}}, so ten units, or 10, must be ten times that, or {{{50/5}}}, {{{50/5}}} and {{{2/5}}} is {{{52/5}}}.  Likewise, 7 and 4/5 must work out to {{{35/5}}} and {{{4/5}}} is {{{39/5}}}


Now subtract 39 from 52 giving you 13, so the result is {{{13/5}}} (You can just add or subtract the numerators because the denominators are the same).  If you need to put the answer back into mixed fraction form, use integer division (that's the kind of division you first learned to do where you would end up with a quotient and a remainder).  The quotient from your division is the whole number part of the mixed fraction, and the remainder over the divisor is the fraction part.  13 divided by 5 is 2 with a remainder of 3, so the final answer is 2 and 3/5.