Question

The perimeter of a triangle is 7a-11b. If two of its sides are 2a+b and a-9b what is the third side?

Answer 1

Let the third side be A
perimeter of triangle = sum of all its three sides
i.e. 7a-11b = 2a+b + a-9b +A
i.e. 7a-11b = 3a-8b +A
i.e. 7a-11b -3a+8b =A
i.e. 4a-3b =A
Therefore third side of the given triangle= 4a-3b