How many class room hours does the typical university teacher teach per week?
There is no “typical” number in this matter. Let's take a few examples:


UK, lecturer: it's usually a full-time position, so you have to put in 35-40 hours per week. The ratio of lecture time over all the rest (preparation, departmental committees, etc.) depends on the contract, but I have rarely seen it pushed past 1:1 (which means roughly 20 hours of teaching, maybe 25 at most).
France, "PRAG": this is the position of a high-School teacher detached to a university, and the closest one to a lecturer position. Their nominal teaching load is 384 hours per year, with a weight of 1.5 for lectures and 1 for exercises sessions. But for one the year is very short, from about 23 to 26 weeks, so that means about 15 hours per week, and this is only the nominal amount. In any cases, they (voluntarily or not) have to teach additional hours, which are paid in addition (to a lower rate than nominal hours).
As a point of comparison: a French high-school teacher would have 18 teaching hours per week.


Other comparison points, less relevant to the question as they are for teaching+research positions:


France, associate professor (maître de conférences): junior-level position, supposed to be half teaching and half research. This has a fixed number of 192 teaching hours per year. If you consider that those are spread on 30 weeks, it gives 6.4 hours per week. Even considering it is not a teaching-only position, that number is lower than the one you quote.
France, full professor (professeur des universités): same number of hours in theory, but as you gain seniority you can do more full-class teaching (with bigger groups), of which every hour counts as 1.5 hour in your yearly total. Through this, and other mechanisms, senior professors usually have fewer hours to teach.