When adding the rule of fractions is where required make all denominators the same by dividing the one you want to change to- by the subset one you are changing.
12 / 4 = 3
we get 3/12
Then when adding same denominators 1/12 + 3/12 we just add the top values. = 4/12
The last box would be 4/12 but if asked to simplify we would automatically enter 1/3 for simplification.
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