Answer:
Insert the math symbols between certain numbers to create an equation:
743  ( =,  -)        Answer :  7 - 4 = 3
6915 ( +, =)       Answer :  6 + 9 = 15
5371 ( -, +, =)    Answer :  5 + 3 - 7 = 1
87654321 ( -, +, -, =)  Answer : 87 - 65 - 4 + 3 = 21
93723522  (+, +, -, =,  -)  Answer : 9 - 37 + 23 + 5 = 2 - 2
2582645  (-, -, =, +, +)  Answer : 25 - 8 - 2 = 6 + 4 + 5