To solve this expression, we can follow the order of operations (PEMDAS/BODMAS) which states that we should perform any calculations inside parentheses first, then any exponents, followed by multiplication and division (from left to right), and finally addition and subtraction (from left to right).

Let's break down the expression step by step:

7,89 : 0,5 = 7.89 ÷ 0.5 = 15.78
15.78 + 7,89 = 23.67

23.67 : 0,2 = 23.67 ÷ 0.2 = 118.35
118.35 + 7,89 = 126.24

126.24 : 0,25 = 126.24 ÷ 0.25 = 504.96
504.96 + 7,89 = 512.85

Therefore, the final result is 512.85.