* what to do:

- Change your clothes.

- Don't talk loudly.

- Do not rummage or touch anything dangerous.

- Do not bring food or drink.

x × 1,25 - x : 5 = 15, 75

=> x ​× 1,25 - x × 1/5 = 15,75

=> x × 1,25 - x × 0,2 = 15,75

=> x × (1,25 - 0,2) = 15,75

=> x × 1,05 = 15,75

=> x = 15,75 : 1,05

=> x = 15

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