A+B+C=（32+36+39）=107
A+B=32*2A+C=36*2B+C=39*22A+2B+2C=32*2+36*2+39*2A+B+C=32+36+39
(32*2+36*2+39*2)÷2=107
(a+b)/2=32(a+c)/2=36(b+c)/2=39三式想加则a+b+c=107
