Your method looks pretty wrong to me, and I don't know why you use H and P instead of the standard x and y.
if you have y = 0.8x
and y = 0.3x + 5
then simply set the two equations equal to each other as you have done:
0.8x = 0.3x +5
subtract 0.3x from both sides gives you: 0.5x = 5
then divide both sides by 0.5 to give you x = 10
then substitute x = 10 into say the first equation: so y = 0.
10) =8
sp y is 8 and x is 10. Check your answer by substituting into the 2nd equation: 8 = 0.3(10) + 5 = 8 it works so you know 100% sure that you are correct. So the lines cross at the point (10,8) as you said....this method works for ANY pair of simultaneos equations with 2 unknowns. If you have 3 unknowns you need 3 equations etc.
[ 01-22-2002: Message edited by: Vaskez ]