33.34 Let $[x]$ denote the greatest integer not exceeding $x$. Then the number of positive integer solutions to the equation $[1.9 x]+[8.8 y]=36$ is
(A) 5.
(B) 4.
(C) 3.
(D) 2.
(China Guangzhou, Wuhan, Fuzhou, and other five cities Junior High School Mathematics League, 1988)
［Solution］Since $x, y$ are positive integers, then first $y \geqslant 1$.
Also, $[8.8 y]<36$, so $y \leqslant 4$. That is, $1 \leqslant y \leqslant 4$.
By substituting $y=1,2,3,4$ into the equation, we find that $(15,1),(10,2),(1,4)$ are its solutions. Therefore, the answer is $(C)$.