z=tdy-7,8t

It looks like you've provided an equation involving variables \( z \), \( t \), and \( y \). However, the equation appears to have some formatting issues or may be incomplete.

Could you clarify what \( z = t \cdot y - 7.8t \) represents? Are you looking to solve for a specific variable, or do you need help with understanding the equation or extending it mathematically? Please provide additional context or specify your question.