Khachaturyan A.v.

A kilogram of beef with bones costs 78 rubles, a kilogram of boneless beef costs 90 rubles, and a kilogram of bones costs 15 rubles. How many grams of bones are there in a kilogram of beef?

#
Let $x$ kg be the weight of bones in a kilogram of beef, then the weight of "pure" beef in it is (1 - $x$) kg. Thus,

$$
15 x+90(1-x)=78
$$

from which $x=0.16$.

## Answer

160 grams.