This is the concept of algebra, To get the total number of stickers Sally had in the end we proceed as follows;
Suppose the initial number of stickers was x;
When she lost 2/3 of the tickets the remaining, the number of tickets that she lost was 2/3x.
The remaining number of tickets will be:
x-2/3x=1/3x
The number of tickets she gave to Paul will be given by:
1/3x*1/4
1/12x
After her brother gave her 120 tickets, the new number of tickets was:
1/12x+120
=(x+1440)/12
The ratio of the original number to the number she ended up with is 4:3, therefore;
x/[(x+1440)/12]=4/3
x*12/[x+1140]=4/3
[12x]/[x+1440]=4/3
cross-multiplying the expression we get:
3*12x=4[x+1440]
36x=4x+5760
32x=5760
dividing both sides by 32 we get:
(32x)/32=5760/32
x=180
Therefore the initial number of tickets was 180 tickets