Applying addition and subtraction strategies within context

Maths

I scored 13, 15 and double 9 on the dart board.  What is my total?

I scored 11, triple 6 and double 8 on the dart board. What is my total?

I scored double 2, triple 10 and a bullseye.  What is my total?

I have 300 points. I have just deducted 87 points. How many points do I have left?

I have 201 points.  I have just deducted 93 points.  How many points do I have left?

To do something well without wasting energy.

Changing the order of the addends to make a calculation easier

Which of these is not a strategy for subtracting efficiently?

When calculating 50 - 48 which is an efficient strategy?

When calculating 92 - 57 which would be an efficient strategy?