With an increase in gas temperature by 10%, its pressure increased by 2 atm. What pressure was the gas under?

Gas pressure is directly proportional to its temperature.

P1 / T1 = P2 / T2;

T2 = 1.1T1;

P2 = P1 + 2 (it is not necessary to convert pressure into system units, since in expression 1 the units of measurement will be reduced);

Substitute the obtained ratios into expression 1:

P1 / T1 = (P1 + 2) / 1.1T1;

1.1P1 = P1 + 2

P1 = 20 atm.

Answer: P1 = 20 atm.