Steps:
1. Length of crown molding on one wall is and on another wall is
2. Total Crown molding done in the total room is
3. As we are having different denominators,
4. We have to take LCD, by listing multiples of denominators as shown
Then, LCD is 8
5. As the denominator is changed, then the numerator also to be changed by the same number, then
6. As the denominator of the second fraction is 8 there is no need to change the denominator.
7. Now the denominators are common, so add numerators
8. Therefore fraction is
Hence, the total Crown molding done in the room isfeet.