if { x } is the product of all even integers from 1 to x inclusive , what is the greatest prime factor of { 18 } + { 16 } ?
soln : { 18 } + { 16 } = 18 * { 16 } + { 16 } = 19 * { 16 } answer : d
add(divide(add(18, 16), const_2), multiply(1, const_2))