In trying to declutter my house, I was looking at some past issues of aviation magazines and came across a chart of average times to solo, as in the Sept. 2005 AOPA mag.
As you'd expect, about 10 to 15 hours was the norm, (most students were in 152 or 172s) with that being 29% of total.
23% took 5 to 10 hours,
21% took 15 to 20 hours
25% took more than 20 hours.
A few, 2% took less than 5!
I recall when I learned in a Piper Cherokee 140 ,it took me 12 hours to solo. I was at a fairly small airport, Montgomery Field in San Diego, but did have a few delays since it had a control tower. A real busy airport, with a tower and lot's of other traffic . especially IFR or airline traffic can make for more delays.
Some years ago, a couple of experienced CFIs wanted to see how quickly they could teach a student from ground zero just to safely fly a solo. The found a lady who new nothing about flying, and taught her in a 152, just for a solo, one takeoff, once around the pattern and one landing; not all the other stuff about navingating, etc.
She was a Las Vegas showgirl, knew nothing about planes.
She did the solo flight after 5 hours.
AOPA used to have a great "PINCH HITTER" program , with actual flying and the students learnig to land their planes. Sadly, the program now is all talk, all classroom, no flying. Interesting, but not nearly as valuable.