At x or at any place same level of x, the pressure is the same.
Say at the left side of x, we can do a equation which looks like this
Total Pressure(at left of x)=P(atm)+P(20cmHG)
Unfortunately, we dont know the atmosphere pressure. Therefore, we can do equation for x
Total pressure(at x)= (70cmHG)+P(20cmHG)
since at same level, pressure is the same, pressure=90cmHG

ok...u are right. im not sitting for exam this year. good luck to u