Greetings from Brasil...
Let's find the equivalent fractions
A/B ; C/D ⇔ A·D/B·D ; C·B/B·D
Bringing to our problem:
A/B ; C/D ⇔ A·D/B·D ; C·B/B·D
1/3 ; 2/5 ⇔ 1·5/3·5 ; 2·3/3·5 ⇔ 5/15 ; 6/15
Now we can sum/add the equivalent fractions
5/15 + 6/15 = 11/15
11/15 to accomodation and food
15/15 = total
total - (accomodation and food) = other purposes
15/15 - 11/15 = 4/15
So 4/15 its the fraction for other purposes
