Answer:
3 hours
Step-by-step explanation:
We have that,
Time spent by Ed to do math homework =
=
hours.
Time spent by Ed to do science homework =
=
hours.
Thus, total time spent by Ed = Time for math + Time for science
i.e. Total time spent by Ed =
+ 
i.e. Total time spent by Ed = 
i.e. Total time spent by Ed = 3 hours.
Hence, the time spent by Ed doing his homework is 3 hours.