Public static int recur (int x) { if (x > = 0) return x + recur (x - 1); return 0; } What is returned by the method call recur (9) ?

9 > = 0 so return 9 + ...

8 > = 0 so return 8 + ...

7 > = 0 so return 7 + ...

6 > = 0 so return 6 + ...

5 > = 0 so return 5 + ...

4 > = 0 so return 4 + ...

3 > = 0 so return 3 + ...

2 > = 0 so return 2 + ...

1 > = 0 so return 1 + ...

0 > = 0 so return 0 + ...

-1 is not > = 0 so return 0.

Now string together all the returns ...

9+8+7+6+5+4+3+2+1+0+0=45

recur (9) returns 45