A+B+B=35.
B+B+c=25.
A+B+B+B+c=55
What is the value of B?
A + B + B = 35
A + 2 B = 35
B + B + C = 25
2 B + C = 25
A + B + B + B + C = 55
A + 3 B + C = 55
You have 3 equations :
A + 2 B = 35
2 B + C = 25
A + 3 B + C = 55
A + 2 B = 35 Subtract A to both sides
A + 2 B - A = 35 - A
2 B = 35 - A
2 B + C = 25 Subtract C to both sides
2 B + C - C = 25 - C
2 B = 25 - C
2 B = 2 B
35 - A = 25 - C Subtract 25 to both sides
35 - A - 25 = 25 - C - 25
10 - A = - C Multiply both sides by - 1
- 10 + A = C
A - 10 = C
C = A - 10
A + 3 B + C = 55
A + 3 B + A - 10 = 55
2 A + 3 B - 10 = 55 Add 10 to both sides
2 A + 3 B - 10 + 10 = 55 + 10
2 A + 3 B = 65 Subtract 3 B to both sides
2 A + 3 B - 3 B = 65 - 3 B
2 A = 65 - 3 B Divide both sides by 2
A = 65 / 2 - 3 B / 2
A + 2 B = 35
65 / 2 - 3 B / 2 + 2 B = 35 Multiply both sides by 2
65 - 3 B + 4 B = 70
65 + B = 70 Subtract 65 to both sides
65 + B - 65 = 70 - 65
B = 5