Beam on three cords loaded by three weights
Tracing how the loads at f and b redistribute among cords a, c, d
A beam hangs from three cords a, c, d and carries three weights, its diagram labelled with the numbers 3 1 7 and 4 4 and the points a b c d f. Leonardo works through the balance: the weight 4 at f offsets 2 at b, and both load onto the pole d, so the 7 at b is reduced to 5. That remaining 5 is then divided among the cords, a and c taking one each while in the second arrangement a takes 2 and d takes one.
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Weight 4 at f balances part of the load at b
Here the weight 4 at f lifts, or stands in balance with, two at b; the 4 at f and the 2 at b both load onto the pole d. So the 7 at b is left as 5, lacking the 2 that the 4 at f took from it.
The remaining 5 divided among cords a, c, d
The remaining 5 divides among the cords a, c, d, as shown: a and c, being equidistant from weight b, take one each. In the second position b d, being double a b, a takes 2 and d takes one.