A commutative ring with unity and Ideals

[emptyboat]

Let R be a commutative ring with unity. I and J are ideals of R.
Show that If I + J = R, then I∩J=IJ.

I know that IJ⊆(I∩J).
But I can't do inverse.

 

[emptyboat]

I solve it!
Thus no answer is required. :)