we know that
In any triangle the sum of the interior angles must be equal to 180 degrees
so
In the first triangle (bottom) we have
64+71+x=180
Solve for x
x is the missing angle
135+x=180
x=180-135
x=45 degrees
The first missing angle is 45 degrees
step 2
triangle of the top
we know that
The first missing angle is 64 degrees by vertical angles
so
we have that
64+56+y=180
solve for y
120+y=180
y=180-120
y=60 degrees