Zach and roger spent a total of 69 hours building a treehouse. roger worked 9 hours less than twice the number of hours zach worked. which system of equations can be used to determine the number of hours zach worked, x, and the number of hours roger worked, y?
a.
x + y = 69
2x + y = 9

b.
x - y = 69
y = 2x + 9

c.
x + y = 69
y = 9x - 2

d.
x + y = 69
y = 2x - 9