Hi
Could someone assist in how 65% for the weight of equity was found from the below, full calculation is not provided?
B sets out the WACC equation and substitutes wd= 1 - we. You end up with one linear equation and one unknown. 
This is a classic example of working in reverse to answer a questions.
If the capital structure in either debt or common equity (assume no prefs)
So weight of debt - weight of equity = 1
Weight of debt = 1 - weight of equity
Pick the middle calue of teh 2 solutions
We = 65% therefore Wd = 35%
Calclate WACC on this basis.
Answer correct so ok.
But if calculated WACC was too low need to increase weight of equity (as cost of equity is higher than cost of debt) and so could have adjusted answert.
i think this is quicker than doing algebra that suggested solution method.