R₁ + R₂ = 90 ...(i) R₁R₂/(R₁+R₂) = 20 → R₁R₂ = 1800 ...(ii)

Solving quadratic x² − 90x + 1800 = 0:

x = (90 ± √(8100−7200))/2 = (90 ± 30)/2

R₁ = 60 Ω, R₂ = 30 Ω