Explanation:
If x is the amount the eldest receives, y is the amount the middle receives, and z is the amount the youngest receives, then:
x + y + z = 656000
x = 6z
y = z + 15000
Substituting the last two equations into the first:
(6z) + (z + 15000) + z = 656000
8z + 15000 = 656000
8z = 641000
z = 80125
Solving for the remaining variables:
x = 6z = 480750
y = z + 15000 = 95125
The eldest receives $480,750, the middle receives $95,125 and the youngest receives $80,125.