Answer:
First 4 subparts are answered below:
A)
Equation for budget constraint: p1.x1 + p2.x2 = M
Substituting the given information gives: 1B + 5P = 20
B)
The budget constraint is below: See attachment
C)
Slope of budget constraint: -P(pizza)/P(beer) = -5
D)
New budget constraint: 2B + 5P = 20
New slope: -5/2 = -2.5
New constraint line: See attachment