Schaum's Outlines contain hundreds solutions to problems covered in any college course. This guide, which can be used with any text or can stand alone, contains a list of key definations, a summary of major concepts, and step by step solutions.
It is not rational to buy expensive textbooks on mathematical economics when you have this book available to you - it is inexpensive, comprehensive and explains things very clearly, what else do you want ? If you have to learn this subject, then at the very least do not spend a fortune on it.
Short briefly with a lot of exercises but it's not in-depth fundamental mathematical economics book like Alpha,Chiang I recommend for freshman who pass calculus 1 and Micro Economics 1 courses even more there're somethings beyond fundamental microeconomics like Cobb–Douglas production function.