Answer:
x = 14
Step-by-step explanation:
An isosceles triangle has a base and two equal legs. Because you know that one of the legs is 3x-5, the other leg is also going to be 3x-5. Knowing this, you can add all of the lengths together and have it equal to 88. Then, it's just a matter of combining and dividing.
x + 3x-5 + 3x-5 = 88
7x -10 = 88
7x = 98
x = 14