Answer:
b = (T - a - c - d) / 3
Step-by-step 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:
Isolate b in order to find out how many points they need in the district match:
They need to score (T - a - c - d)/3, in the district match in order to win.