It probably didn't occur to you to put a parentheses 
between the two digits of 16, separating it into a 1
and a 6.  It also may not have occurred to you to
put a parentheses before the -4 making it a multiplied
"negative four" rather than a "subtracted four". 

1(6(-4/2)+3*(3+7))   <--- answer

which equals

1(6(-2)+3*(3+7))

1(6(-2)+3*(10))

1(-12+3*(10))

1(-12+30)

1(18)

18

Edwin