In order to subtract one fraction from another, we need to make the denominator the same in both fractions. The lowest common denominator is 8, because 4 is a factor of 8.
In order to make the denominators the same, multiply both the numerator and denominator of 13/4 by two. This keeps the value of the fraction the same, but will equate the denominators.
[tex] \frac{13*2}{4*2} = \frac{26}{8} [/tex]
At this point, we can simply subtract 5/8 from 26/8.
[tex] \frac{26}{8}- \frac{5}{8} = \frac{21}{8} [/tex]
21/8 cannot be simplified, so it is the answer.
