17. my friend is quite well . she can do it again

my friend is.........well enough to do it again..............

18.she doesn't explain this exericise.his pupils can't do it

she doesn't explain this exericise, so his pupils can't do it

19.there isn't enough time.this student can't write this essay

there isn't enough time for this student to write this essay

20.it's warm tonight.we can go out

it's warm tonight enough for us to go out