(a) \frac{(5-j 6)-(2+j 8)}{(-3+j 4)(5-j)+(4-j 6)}
(b) \frac{\left(240 \angle 75^{\circ}+160 \angle-30^{\circ}\right)(60-j 80)}{(67+j 84)\left(20 \angle 32^{\circ}\right)}
(c) \left(\frac{10+j 20}{3+j 4}\right)^{2} \sqrt{(10+j 5)(16-j 120)}
(a) \frac{(5-j 6)-(2+j 8)}{(-3+j 4)(5-j)+(4-j 6)}
(b) \frac{\left(240 \angle 75^{\circ}+160 \angle-30^{\circ}\right)(60-j 80)}{(67+j 84)\left(20 \angle 32^{\circ}\right)}
(c) \left(\frac{10+j 20}{3+j 4}\right)^{2} \sqrt{(10+j 5)(16-j 120)}
(a) \frac{3-\mathrm{jl} 4}{-7+\mathrm{jl} 7}=\frac{14.318 \angle-77.91^{\circ}}{18.385 \angle 112.38^{\circ}}=0.7788 \angle 169.71^{\circ}=\frac{-0.7663+\mathrm{j} 0.13912}{-10}
(b) \frac{(62.116+j 231.82+138.56-j 80)(60-j 80)}{(67+j 84)(16.96+j 10.5983)}=\frac{24186-j6944.9}{246.06+j 2134.7}=-1.922-j 11.55
(c) (-2+j 4)^{2} \sqrt{(260-j 120)}=\left(20 \angle-126.86^{\circ}\right)\left(16.923 \angle-12.38^{\circ}\right)
=338.46 \angle-139.24^{\circ}=-256.4-j 221