I think you forgot to attach a pic.
What I got was 9/10 or you could make it into a percentage 90% hope this helps
Both are 1/2 because there is two sides so half the time it would be heads and half would be tails
H = height of triangle
b = length of triangle base
A = area of triangle
Recall the formula for area of a triangle :
A = 1/2 bh
Plug in what was given in the problem :
h = b - 5
A = 42
A = 1/2 bh
42 = 1/2 b (b-5)