$$2$$ beds and $$4$$ chairs have a total mass of $$240$$$$\text{kg}$$. $$1$$ bed weighs as much as $$6$$ chairs. Find the mass of $$1$$ chair. 
Overseas In-curriculum->Knowledge Point->Algebra-> Numbers, Letters and Equations->Equivalent Substitution->Direct Substitution Overseas Competition->Knowledge Point->Counting Modules
$$240\div16=15\text{kg}$$ 