Trying to rework on the same model your child drew. By P6, these model drawing increases in complexity as they are split into Unknown blocks and Constants blocks for movement.
With practice and understanding, kids should internalise and use simple algebra of “U”s and Constants to work out the solution and that is when some may selectively drop model drawings totally.
That being said, it is still good to practice both ways (only when model is quite simple. I don’t suggest forcing model when it gets too complex) so kid will continue to reinforce both visual and abstract understanding. Model drawing is still the fundamental of understanding and could sometimes be (surprisingly) the easiest way out for solving.
For illustration only (notice we let Eton be 3u+30 for ease of spliting for 1/3 like model)
J = 3u J = 3u + u +10
E = 3u + 30 –> 1/3 is u + 10 E = 2u + 20
Diff = 2u + 10-20 = 12 —> u = 11