What is the correct inflation pressure for hybrid road/city bike?
When you take the tire off to fix the puncture- find where the hole(s) are. If there are 2 holes approx the rim width apart, then you have a pinch flat. If it is just one hole, then its probably glass/thorn etc. You will get punctures from glass/thorn no matter what pressure you run at.

Once you have checked, if it's a double hole- run your pressures higher, suggest you look at your tyre and run just below the max (eg. if max is 100 psi (7 bar), run at 90 (6.2 bar). If you run them at the max pressure, it can feel very "hard" on the road (but is used for maximum efficiency) 

If it's a single hole- then looking at tyres with Kevlar/other puncture protection would be a good idea (especially if it continues to happen).