Question

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

Answer 1

To find the missing side we need to calculate the sum of the two given sides and then subtract that from the perimeter.

7a - 11b - (2a + b + a - 9b)

= 7a - 11b - (3a - 8b)

= 7a - 3a - 11b + 8b

= 4a - 3b