Graph of three variables and trendline equation

I want to plot a graph of three variables and to add trenline to it.
PRESSURE HEAD
A(cm)
1) 76
2) 68
3)51.5
4) 40
5) 28
B (cm) PRESSURE HEAD
1) 73
2) 65
3) 48.5
4) 37
5) 24
V(m/s)VELOCITY
1) 0.30
2) 0.29
3) 0.26
4) 0.24
5) 0.19 5) 0.19 Untitled.png
i want to plot a graph and to get equation of 'V' IN TERMS 'A' AND 'B'
I tried but didnt get it.
Plz help