Let the 3 forces be F and G (upwards) and H (downwards).

We are told F + G = H .....(1)

Also, the second force is `6.4` more than the first, `G = F + 6.4` .....(2)

For the third (downwards) force, `H = 4 xx F` .....(3)

If we substitute equations (2) and (3) into (1), we have:

`F + (F + 6.4) = 4F`

`2F + 6.4 = 4F`

`6.4 = 2F`

So `F = 3.2`

This gives `G = 9.6` and `H = 12.8`.

Checking:

(1) `F + G = 3.2 + 9.6 = 12.8 = H` (OK)

(2) `F + 6.4 = 3.2 + 6.4 = 9.6` (OK)

(3) `4F = 4 xx 3.2 = 12.8` (OK)

So the three forces are `3.2` N, `9.6` N and `12.8` N, respectively.

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