Explanation:
0.7 birdhouses in 1 day.
how many in 10 weeks ?
for that we need to know how many days are in 10 weeks.
1 week = 7 days
assuming that she is working on the birdhouses also on weekends, that means 10 weeks = 10×7 = 70 days.
and that means she can build
0.7 × 70 = 49 birdhouses in 10 weeks.
now, if she works only Monday to Friday on the birdhouses, then that means
1 week = 5 days
and 10 weeks = 10×5 = 50 days.
and that means she can build
0.7 × 50 = 35 birdhouses in 10 weeks.
if there is really no other information about that, I would use the usual 7 days per week and the first solution (49).