Question

One third the cost of dinner

Answer 1

Say:
If dinner equals x, the equation would be 1/3x

Answer 2

one third is equal to 1/3 and dinner, or d, is being multiplied by 1/3. So the expression is 1/3d. It can also be written as d/3, because if you want to find a third of a number, then you could divide it by 3

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sorry if I didn't help