she made x buns
she sold 3/5x in morning
she had 2/5x left after morning
in afternoon, she sold 1/4 of what was left or 1/4 of 2/5x or 2/20x or 1/10x
if sold 200 more in morning than in afternoon, find x
basically
morning=200+afternoon
3/5x=200+1/10x
find x
multiply both sides by 10 to get rid of the nasty fractions
6x=2000+x
minus x both sides
5x=2000
divide both sides by 5
x=400
she made 400 buns