已知被减数，减数和差三个数的和是612，求被减数是多少?

a-b=c
a+b+c=612
a+b+(a-b)=612
2a=612
a=306

612÷2=306

612÷2=306

The sum of the three numbers known to be reduced, reduced, and difference is. Do you know what the reduction is?