Hello, Tzuyu,
This just requires a conversion factor. It should be in your books or notes. Google "mmHg to atm" and you'll find many references to the fact that:
1 atm = 760 mmHg
Make that into a conversion factor by dividing by one of the two sides. That gives the choice of two conversion factors, both equivalent, but with differing unit locations:
(1 atm)/(760 mmHg), or
(760 mmHg)/(1 atm)
We can use either one, but the first is my choice. By multiplying the two, the unit mmHg cancels, leaving just atmospheres. If we used the second, we'd need to divide:
(782 mmHg)/(760 mmHg)/(1 atm)
I dislike division to begin with, and since the first allows me to multiply 1 times 766, I can do it in my head.
Therefore,
(782 mmHg)*((1 atm)/(760 mmHg) = 1.029 atm
Bob
