The first set of buying price:120 ÷ (1+20%) =100 (yuan), earned: 100× 20% = 20 (yuan).

The second set of buying price:120 ÷ (1-20%) =150 (yuan), loss: 150× 20% = 30 (yuan).

30-20 = 10 (yuan)

Obviously, this business lost money 10 yuan.