(1) We do not know the value of y. Insufficient.
(2) We do not know the value of x. Insufficient.
Together, x < (64/72), y < (9/72). Choosing values smaller than these results in x+y < 1. Sufficient.
My answer is C
x < 8/9 = 0.88888 ...repeated decimal
y < 1/8 = 0.125
i don't know if it is valid but if we take:
x = 0.12 < 0.125
y = 0.88 < 0.888888
x+y = 1.00
in this case ans will be E.
however as i said, i am not sure about bold part