Question

{42+[(45-19)-(18-3)+1]-(28-15)-1}

Answer 1

{42+[(45-19)-(18-3)+1]-(28-15)-1} =
{42+[(26)-(15)+1]-(13)-1} =
{42+[26-15+1]-13-1}=
{42+[12]-13-1} =
{42+12-13-1} =
40