By the angle bisector theorem, one of the lengths of the third side of the triangle is given by:
1.5 / 1 = x / 2.6
x = 1.5 x 2.6 = 3.9
One of the possible length of the third side is 3.9 cm
The other possible length is given by 1 / 1.5 = x / 2.6
1.5x = 2.6
x = 2.6/1.5 = 1.7
The other possible length of the third side is 1.7 cm.
See how there are two rectangle prisms? Find the area of both of them separate, and then add the two answers together.
Hope this helps!!