I believe the answer is this but am not sure:
49+6-3(71*21)/15+7^3
Parenthesis: 71*21=1491
49+6-3*1491/15+7^3
Exponent: 7^3=343
49+6-3*1491/15+343
Multiply: 3*1491=4473
49+6-4473/15+343
Divide: 4473/15=298.2
49+6-298.2+343
Add: 49+6=55, 298.2+343=641.2
55-641.2
Subtract: 55-641.2=-586.2
Final Answer: -586.2