You have buckets of 3 L, 7 L

MATHEMATICS · Multi-part · AoPS · Mathematics · One-Variable Linear Equations · Linear Equations in Disguise

Problem

You have buckets of 3 L, 7 L, and 20 L. How can you measure exactly: 10 L, 4 L, and 5 L? (1) 10 L (2) 4 L (3) 5 L