Answer: red is 21, green is 14 and blue is 7
Explanation:
Let r represent the length of the red stick.
Let g represent the length of the green stick.
Let b represent the length of the blue stick.
The red one is three times as long as the blue. This means that
r = 3b
The green one is 7 inches longer than the blue. This means that
g = b + 7
The blue and green together are the same length as the red. This means that
b + g = r
g = r - b
Therefore
b + 7 = r - b
r = b + b + 7 =2b + 7
Substituting r= 3b into r = 2b + 7, it becomes
3b = 2b + 7
3b - 2b = 7
b = 7
r = 3b = 3 × 7 = 21
g = b + 7 = 7 + 7 = 14