Question

please give me the answer​

Answer 1

here given x+y=4then x=4-y put this value in first equation you will get the answer

Answer 2

Here
x+y = 4
CUBING BOTH SIDES ...
( x+y )³ = 64
x³+y³+3xy(4) = 64
x³+y³+12xy= 64
x³+y³+12xy-64
HENCE PROVED...