Are you sure you don't mean: the 2 orca whales add up to 13,000 lbs?

Because I'm getting an odd answer...

Let

be the weight of a beluga whale

Let

be the weight of an orca whale

You know: "The weights of two beluga whales and 3 orca whales add up to 36,000 pounds"

So:

And: "...one of the orcas add up to 13,000 lbs."

So

We have 2 orca whales, so their weight is two times the weight of one.

So its weight is:

.

Use the value of

to get the weight of one beluga whale.

A negative weight? I don't see how... ?