The average of three rocks is 26 pounds.

Question

The heaviest is twice as heavy as the lighest. The lighest rock is two pounds less than the middle rock. How much is the lightest rockc

Answer 1

l=lightest

m=middle

h=heaviest

 

l=m-2

m

h=2l

(l+m+h)/3=26

l+m+h=3*26

l+m+h=78

substitute

m-2+m+2l=78

2m+2l-2=78

2m+2l=78+2

2m+2l=80

m+l=40

substitute again

m+m-2=40

2m-2=40

2m=2+40

2m=42

m=21

l=21-2

l=19

h=2l

h=2*19

h=38

lightest=19 pounds, middle=21 pounds, heaviest=38 pounds