Answer
7.5$^{\circ}$
Work Step by Step
1.$\frac{360^{\circ}}{12}= 30^{\circ}$
A clock is a circle, therefore has 360$^{\circ}$. When we divide on 12 we find degrees in each hour
2. $\frac{1}{4}\times$ 30 = 7.5$^{\circ}$
A distance between minute and hour hand at 3:15 is very small. As hour hand already passed 15/60 of the road to the 4 o clock, the degrees in one hour should be multiplied to the 1/4.