So there are 3 siblings: the first twin, the second twin, and their older sister.
Since the sister is older by 11 years, you can represent their relationship with the following equation;
age of twin = age of older sister - 11
t = s - 11
Representing this next part may be a little hard to show, but i'll do my best :)
Adding the ages together can be represented like this;
total age = t + t + s
If the product of their ages ( t * t * s ) is 1181 more than the sum, you can show it like this:
![t * t * s = (t + t + s) + 1181](https://tex.z-dn.net/?f=t%20%2A%20t%20%2A%20s%20%3D%20%28t%20%2B%20t%20%2B%20s%29%20%2B%201181)
Now you substitute in (s - 11) for t because s = t - 11.
![t * t * s = (t + t + s) + 1181\\ (s-11) * (s-11) * s = ((s-11) + (s-11) + s) + 1181\\ (s^{2}-22x+121)*s=s+s-11-11+1181\\ s^{3}-22s^{2}+121s-2s=1159\\ s^{3}-22s^{2}+118s-1159=0](https://tex.z-dn.net/?f=t%20%2A%20t%20%2A%20s%20%3D%20%28t%20%2B%20t%20%2B%20s%29%20%2B%201181%5C%5C%0A%28s-11%29%20%2A%20%28s-11%29%20%2A%20s%20%3D%20%28%28s-11%29%20%2B%20%28s-11%29%20%2B%20s%29%20%2B%201181%5C%5C%0A%28s%5E%7B2%7D-22x%2B121%29%2As%3Ds%2Bs-11-11%2B1181%5C%5C%0As%5E%7B3%7D-22s%5E%7B2%7D%2B121s-2s%3D1159%5C%5C%0As%5E%7B3%7D-22s%5E%7B2%7D%2B118s-1159%3D0)
Factor:
Since it's a third-degree equation, I just entered it into a polynomial solver in my calculator. There was only one factor listed, x = 19. Using (s - 19) = 0 as a factor, the equation becomes the following:
![s^{3}-22s^{2}+118s-1159=0\\ (s-19)(s^{2}-3s+61)=0](https://tex.z-dn.net/?f=s%5E%7B3%7D-22s%5E%7B2%7D%2B118s-1159%3D0%5C%5C%0A%28s-19%29%28s%5E%7B2%7D-3s%2B61%29%3D0)
Using the quadratic formula, you get:
![s= \frac{-b(+-)\sqrt{b^{2}-4ac}}{2a}\\ s= \frac{-(-3)(+-)\sqrt{(-3)^{2}-4(1)(61)}}{2*1}\\ s= \frac{3(+-)\sqrt{(9)-244}}{2}\\ s= \frac{3(+-)\sqrt{-235}}{2}](https://tex.z-dn.net/?f=s%3D%20%5Cfrac%7B-b%28%2B-%29%5Csqrt%7Bb%5E%7B2%7D-4ac%7D%7D%7B2a%7D%5C%5C%0As%3D%20%5Cfrac%7B-%28-3%29%28%2B-%29%5Csqrt%7B%28-3%29%5E%7B2%7D-4%281%29%2861%29%7D%7D%7B2%2A1%7D%5C%5C%0As%3D%20%5Cfrac%7B3%28%2B-%29%5Csqrt%7B%289%29-244%7D%7D%7B2%7D%5C%5C%0As%3D%20%5Cfrac%7B3%28%2B-%29%5Csqrt%7B-235%7D%7D%7B2%7D)
Since you have a square root of a negative number, the answer will be imaginary. You cannot have an age that is imaginary, so the age of the older sister (s) is 19 years.
Because t = s - 11, that means that t = (19) - 11 = 8.
t is the age of the twins, so the twins are
8 years old.