Solve for a and b. 2a-ai-5b=0, a-2b-bi=0. Where i is complex number.

2a - 5b = ai ------> 2a-5b=ai

a - 2b = bi (times2), 2a - 4b = 2bi

subtract:
-b = ai - 2bi
b = 2bi - ai

sub in a-2b = bi
2bi-ai - 2b = bi
bi - 2b = ai
b(i-2) = ai
b = ai/(i-2)
= ai/(i-2) * (i+2)/(i+2)
= (ai^2 + 2ai)/5
= (-a + 2ai)/5