At the start of my tuition, I always write 'helpful' notes next to each type within the test that is left for homework. For type K bracket maths, I write the following:
Middle number has been made using the numbers either side.
Same rule must apply for all 3 sets.
Sometimes 1 operation. Sometimes 2.
Second operation can be:
1] + - x / [divide sign!] the same number.
3] + - x / [divide sign] the number on the left or right of the middle number.
Whilst teaching, I always say:
If the number in the middle is bigger than the 2 either side then your 1st operation is probably adding or multiplying.
If the number in the middle is smaller that at least one of the numbers either side, then your 1st operation is probably subtracting or dividing.
I always emphasise the word probably, because there are times when this rule will not work, they are not to panic, if it doesn't work, thats fine, just try the other 2 operations.