Jumping from a moving wagon momentum problem -- find Buffy's weight

[Jujubee37]

Homework Statement

Buffy is rolling along in her 11.8 kg wagon at 3.8 m/s (in the positive direction) when she jumps off the back. She continues to move forward at 1.8 m/s relative to the ground. This causes her wagon to go speeding forward at 8.87 m/s relative to the ground. How much does Buffy weigh?

Relevant Equations

n/a

I have attempted to plug in grams, kiliograms, and even pounds but it was wrong.

 

[TSny]

In everyday life, we often see "weight" given in grams or kilograms. However, in physics, the gram and the kilogram are units of mass while weight is associated with the force of gravity. What is the unit of force in the SI system?

 

[Orodruin]

Homework Statement:: Buffy is rolling along in her 11.8 kg wagon at 3.8 m/s (in the positive direction) when she jumps off the back. She continues to move forward at 1.8 m/s relative to the ground. This causes her wagon to go speeding forward at 8.87 m/s relative to the ground. How much does Buffy weigh?
Relevant Equations:: n/a

I have attempted to plug in grams, kiliograms, and even pounds but it was wrong.

Attempted to plug in into what? We do not know what formula or even concept you are trying to use. As such it is impossible to pinpoint where you are going wrong.