8k-7,78k=0,4488

Assuming comma is the decimal separator:

• 8k - 7,78k = 0,4488 becomes 8k - 7.78k = 0.4488
• (8 - 7.78)k = 0.4488 → 0.22k = 0.4488
• k = 0.4488 / 0.22 = 2.04

So, k = 2.04 (exactly 561/275).