math
posted by lomas .
there are 4 girls in Mrs. Changs class than Mr. Blackwell's.
5 girls moved from Mrs. Changs to Mr. Blackwells.
Now there are twice as many girls in Mr. Blackwells class as there are in Mrs. Changs, How many girls were in Mr. Blackwells class to begin with?
Help, stuck with this problem.

retype the first sentence, it makes no sense and must contain a typo ....
probably "4 more girls" or "4 less girls" 
sorry. it's 4 more girls

make a chart:
Now....
Mr Blackwell  x students
Mrs Chang  x+4
after move:
Mr. B  x+5
Mrs. C  x1
x+5 = 2(x1)
x+5 = 2x  2
x = 7
so Mr B had 7, Mrs C had 11
(Wow! 7 students and 11 students, where do these schools exist ???? I might go back to teaching) 
thank you.