5100 * 7 = <<5100*7=35700>>35,700 pounds
1 ton = <<2000=2000>>2000 pounds
8 * 2000 = <<8*2000=16000>>16000 pounds
35,700 + 16,000 = <<35700+16000=51700>>51,700
Seven white rhinos and 8 black rhinos would weigh 51,700 pounds.
#### 51700