I will set up each proportion but you must do the math work.
Part a.
Let s = souvenirs
8/26 = 12/s
Solve for s to find your Part a answer.
Part b.
Let x = snacks
10/x = 20/5
Solve for x to find your Part b answer.
Part c.
Here we must create two proportions.
For Sinea:
Let y = souvenirs
5/40 = 12/y
Solve for y to find how much Sinea spend on souvenirs.
Let k = souvenirs
10/4 = 20/k
Solve for k to find how much Ren spend on souvenirs.
When you find y and k for Part c, subtract the smaller value from the bigger value to find your answer.