4. The sum of several addends is equal to \(2 b-1\). To one addend, \(3 b-8\) was added, and from the second, \(-b-7\) was subtracted. How much must be subtracted from the third addend so that the sum becomes equal to zero?
4. Solution. If \(x\) is the desired number, then

\(2 b-1+(3 b-8)-(-b-7)-x=0 ; x=6 b-2\).