(18² - 1/2²):(18✓1/2)=(18²-1/4)x(1/18✓1/2)= 4x18²-1/4x1/18x1/✓2=4x324-1/4x1/18/✓2=
1296-1/4x✓2/18=1295/4x✓2/18=1295✓2/72