Answer:
![b=(T-a-c-d)/(3)](https://img.qammunity.org/2021/formulas/mathematics/high-school/sgt5ad0plxu5ko90j77qlkv4ethju408tn.png)
b = (T - a - c - d) / 3
Explanation:
Let T be the total number of points required to advance.
a, c and d are points scored in the local matches, and b is the number of points scored in the district match. If b is worth 3 times as much as the other matches, the total number of points is given by:
![T=a+c+d+3b](https://img.qammunity.org/2021/formulas/mathematics/high-school/zjsfyg09069s1gqqtowl07etmalg1xvhfn.png)
Isolate b in order to find out how many points they need in the district match:
![T=a+c+d+3b\\3b=T-a-c-d\\b=(T-a-c-d)/(3)](https://img.qammunity.org/2021/formulas/mathematics/high-school/ahu4i1o7wjyae5mmyep33wrh6becb3qvja.png)
They need to score (T - a - c - d)/3, in the district match in order to win.