[(⅕)⁻² * (1⅔)⁻¹ - (3¹ - 2⁻¹)⁻² ] / (2/21)⁻¹ = ... = -2

[5²*(5/3)⁻¹-(3-1/2)⁻²]:21/2=[25*3/5-(3-1/2)⁻²]:21/2=[15-(2½)⁻²]21/2=[15-(5/2)⁻²]:21/2=[15-(2/5)²]:21/2=[15-4/25]*2/21=14i 21/25*2/21=724/525