Maybe it's a little too hard. Let me help you on the way a bit.
Example:
From the solutions to the upper left-most equations, you could deduce that symbols standing next to each other have to be added, since 19 is a prime number.
Then if you choose the following values for the small square, triangle and diamond, square = 1, triangle = 10, diamond = 6, the upper left-most equation is solved.
Moving on to the equation below that one. If you choose the Fibonacci function for the big circles, you get Fib(6) + 10 + Fib(1) = 19, which is correct as well, since Fib(6) yields 8 and Fib(1) = 1.
Of course this isn't the correct solution, I'm just showing you how it might be done.
The big symbols could stand for all kinds of functions, e.g. squares, cubes, square roots, prime numbers, triangular numbers, factorials, etc.
Koko