A+B = 12, A+B+C = 8 then find C?

A+B = 12, A+B+C = 8 then find C?

Explanation

 We know A + B = 12.

We also know A + B + C = 8.

Substitute the value of A + B into the second equation: 12 + C = 8.

Solve for C: C = 8 - 12 = -4.