Answer: see below
Step-by-step explanation
Let 2 + a = 11 x
Let 35 - b = 11 y
Where x and y are any unknown integer
subtract the two equations
- 33 + a + b = 11 (x+y)
a+ b = 11 (x+ y) +33
a+ b = 11 (x+y) + 3 (11)
a+ b = 11(x+ y+3)
Which proves that a+b is a factor of 11