45 minutes corresponds to [tex] \frac{3}{4} [/tex] of hour. There are 25 waves per hour, so we must find how many waves there are in [tex] \frac{3}{4} [/tex] of hour. Therefore we can write the following proportion:
[tex]25 waves: 1h = x : \frac{3}{4} h[/tex]
and by solving ,we find
[tex]x= \frac{25 \cdot \frac{3}{4} }{1 }=18.75 waves [/tex]
So, the surfer should expect almost 19 waves in 45 minutes.
