R+C =10 equation 1
R +D= 20 equation 2
C+D= 24 equation 3
R+C+D=?
Solution;
Equation 2 - Equation 1 R+D = 20
-R+C= 10
Result
D-C=10 or D=10+C
Substitute the result to
Equation 3 C+(10+C)=24
2C=24-10
C=7
Substitute C to Equation 1
R+7=10
R=3 Substitute R to Equation 2
D+3=20
D=17 So,
R+C+D=?
3+7+17=27