In a quantity of gunpowder the composition is:

Nitre: 10 lbs. more than 2/3 of whole.

Sulphur: 4 1/2 lbs. less than 1/6 of whole.

Charcoal: 2 lbs. less than 1/7 of nitre.

Suggestion:

Let x = whole

Nitre: 2/3x + 10

Sulphur: 1/6x - 4 1/2

Charcoal: 1/7(2/3 + 10) - 2

Unsure how to continue.