$1-\frac {1} {2}\times \frac {2} {3}=$

$28\times \frac {4} {7}\times \frac {1} {4}=$

$2\times \frac {2} {5}\times \frac {1} {4}=$

$3\times \frac {4} {3}\times \frac {1} {2}=$

$15\times left ( {\frac {1} {3}+\frac {1} {5}} ight )=$

$\frac {1} {3}\times \frac {3} {5}\times \frac {1} {2}=$

$12\times left ( {\frac {1} {3}-\frac {1} {4}} ight )=$

$\frac {4} {15}\times \frac {5} {6}\times \frac {1} {2}=$