Multiplying by zero always gives zero, so that simplifies your question, which becomes 40+1 which is of course 41. But you knew that! The order of operations when there are no brackets (which take top priority) is that multiply and divide are to be calculated first (multiply and divide have equal priority) before addition or subtraction (which also have equal priority). If there are brackets, calculate what's in the innermost brackets first and work outwards until you've done all the calculations in brackets then carry on with the calculation when you're left with the operations multiply, divide, add and subtract. BODMAS is an acronym for priorities, highest first, standing for Brackets, Of, Divide, Multiply, Add, Subtract.