20- 1= 19
20+ 1=20
First, determine that three consecutive numbers are:
19、20、2 1.
Next, you can add and subtract between these three numbers, adding a few to one number and subtracting a few from the other two numbers.
You can get:
14+ 15+3 1=60
13+ 16+3 1=60
12+ 17+3 1=60
……
1+28+3 1=60
14+ 16+30=60
13+ 17+30=60
……
1+29+30=60
14+ 17+29=60
……
3+28+29=60
14+ 18+28=60
……
5+27+28=60
14+ 19+27=60
……
7+26+27=60
14+20+26=60
……
9+25+26=60
14+2 1+25=60
……
1 1+24+25=60
14+22+24=60
13+23+24=60
……
For reference.