Quaddle

Tired of the same old games that put letters into words? Try to play with digits!
This is an exciting puzzle game for those who like math and got used to games like sudoku. Try to arrange the available digits on the sides of the big square so that each side becomes a true equality (clockwise, taking into account the priority of operations).
When you start a new game, you are given a few "fixed" digits (green) and arithmetic signs (yellow), which cannot be moved. Your task is to use the available "movable" digits (grey) to fill the empty cells (dark grey) of the big square. These digits can be freely interchanged with each other, or be moved over to other free cells.
When you feel it's getting too long to get to a solution, do not worry: after a little while you will be given a few hints (up to 3 for every game) that will make your task easier.