I understand that you need to know what is 3/10 out of 7/8 of an hour: this will tell you how many minutes those two activities last together (we have no information to know how long they last separately).
For this, we need to multiply the two numbers: [tex] \frac{3}{10} * \frac{7}{8} [/tex]
This is equal to:,
[tex] \frac{3*7}{10*8} = \frac{21}{80} [/tex]
if we want to know how many minutes that was; we need to mupltiply this number by 60, the amount of minutes in an hour:
[tex] \frac{21*60}{80}= \frac{64}{4} =15 \frac{3}{4} [/tex]
which is 15.75 minutes
