4. Choose any two numbers from the eight digits $2,4,6,7,8,11,12,13$ to form a fraction. Among these fractions, there are $\qquad$ irreducible fractions.
荟莍 36 .
Analysis: Selecting one integer from $7,11,13$ and one integer from $2,4,6,8,12$ to form a reduced fraction, there are $2 C_{3}^{1} C_{5}^{1}=30$ ways; selecting two integers from $7,11,13$ to form a reduced fraction, there are $A_{3}^{2}=6$ ways, totaling 36 different reduced fractions.