The area of a rhombus is the product of the diagonals divided by 2. In this question, the diagonals are given, so that's really easy. Let's convert the measures to meters, that'll help for the final area calculation:
Area of one rhombus: (0.52x0.30)/2 = 0.078 m²
In 60 m², you can fit 60/0.078 tiles. That's 769.23, rounded to 770 since you'll have to cut up the last tile.