Hello, aquajam!

Imagine the symbols below to sit on balance scales.

Scales 1 and 2 are perfectly balanced.

. .

. .

. .

How many diamonds are needed to balance [3]

From [1], we have: .

From [2]. we have: .

Equate [4] and [5]: .

Substitute into [4]: .

Substitute into [3]:

. . . . .

. .

. . . . . . .

Therefore, 8 Diamonds are needed.