As of my knowledge, there is no specific GPT-4 app dedicated solely to math problem-solving. However, there are several AI-powered math solvers available that can assist you in solving math problems. Some popular options include:

1. Wolfram Alpha: It is a powerful computational knowledge engine that can solve a wide range of math problems, including algebra, calculus, statistics, and more.

2. Photomath: This app allows you to take a picture of a math problem, and it provides step-by-step solutions and explanations.

3. Mathway: It is an AI-powered math problem solver that covers various math topics, including algebra, calculus, trigonometry, and more.

4. Symbolab: This platform offers step-by-step solutions to math problems, including algebra, calculus, statistics, and more.

These AI-powered math solvers can be accessed through their respective websites or mobile apps.