Answer:
35 [$]
Step-by-step explanation:
1) if Peter's sum is p and Jacky's is j, then the ratio 5:2 in the condition can be written j/p=5/2;
2) the phrase 'after Jacky gave 15 dolls to Peter, they have an equal number of dolls' can be written as j-15=p;
3) using the two above it is possible to make up the system of two equations:
4) finally, the have together 10+25=35 doll-s.