If the answer is:28

The question could be...

20+8=28

10+10+8=28

30-10+8=28

15x2=28

2x15=28

40-20+8=28

50-30+8=28

24+4=28

60-40+8=28

70-50+8=28

80-60+8=28

90-70+8=28

100-80+8=28

102-90+8=28

103-100+8=28

104-102+8=28

105-103+8=28

106-104+8=28

107-105+8=28

108-106+8=28

109-107+8=28