Finding value using formulas,functions or macros from intersection of 2 data series

[FONT=&quot]Good afternoon ,I am trying to solve a problem with two data series in a graph where I need find the interception of the two series and find automatically a value .The problem is more easy to understand if is seen the examples book that I attach to the post , [/FONT][FONT=&quot]I am trying to generate automatically the value 1.8 in the example 1 ,21.5 in the example 2 , 65 in the example 3 and 0 in the example 4.[/FONT] [FONT=&quot]Someone can help me please? I'll be very grateful for any help.[/FONT]